diff --git a/fuzzterm.c b/fuzzterm.c
index 255fc6fb..707c4ae8 100644
--- a/fuzzterm.c
+++ b/fuzzterm.c
@@ -88,7 +88,6 @@ void set_raw_mouse_mode(void *frontend, int m) { }
 void request_paste(void *frontend) { }
 void do_beep(void *frontend, int a) { }
 void sys_cursor(void *frontend, int x, int y) { }
-void fatalbox(const char *fmt, ...) { exit(0); }
 void modalfatalbox(const char *fmt, ...) { exit(0); }
 void nonfatal(const char *fmt, ...) { }
 
diff --git a/pscp.c b/pscp.c
index 210362df..87a760c2 100644
--- a/pscp.c
+++ b/pscp.c
@@ -91,21 +91,6 @@ static void tell_user(FILE *stream, const char *fmt, ...)
 /*
  *  Print an error message and perform a fatal exit.
  */
-void fatalbox(const char *fmt, ...)
-{
-    char *str, *str2;
-    va_list ap;
-    va_start(ap, fmt);
-    str = dupvprintf(fmt, ap);
-    str2 = dupcat("Fatal: ", str, "\n", NULL);
-    sfree(str);
-    va_end(ap);
-    tell_str(stderr, str2);
-    sfree(str2);
-    errs++;
-
-    cleanup_exit(1);
-}
 void modalfatalbox(const char *fmt, ...)
 {
     char *str, *str2;
diff --git a/psftp.c b/psftp.c
index e4e77c3a..643389da 100644
--- a/psftp.c
+++ b/psftp.c
@@ -2442,20 +2442,6 @@ static int verbose = 0;
 /*
  *  Print an error message and perform a fatal exit.
  */
-void fatalbox(const char *fmt, ...)
-{
-    char *str, *str2;
-    va_list ap;
-    va_start(ap, fmt);
-    str = dupvprintf(fmt, ap);
-    str2 = dupcat("Fatal: ", str, "\n", NULL);
-    sfree(str);
-    va_end(ap);
-    fputs(str2, stderr);
-    sfree(str2);
-
-    cleanup_exit(1);
-}
 void modalfatalbox(const char *fmt, ...)
 {
     char *str, *str2;
diff --git a/putty.h b/putty.h
index 0dd48a5a..ba7e123a 100644
--- a/putty.h
+++ b/putty.h
@@ -642,10 +642,8 @@ void optimised_move(void *frontend, int, int, int);
 void set_raw_mouse_mode(void *frontend, int);
 void connection_fatal(void *frontend, const char *, ...);
 void nonfatal(const char *, ...);
-void fatalbox(const char *, ...);
 void modalfatalbox(const char *, ...);
 #ifdef macintosh
-#pragma noreturn(fatalbox)
 #pragma noreturn(modalfatalbox)
 #endif
 void do_beep(void *frontend, int);
diff --git a/terminal.c b/terminal.c
index d5d5314a..96a00266 100644
--- a/terminal.c
+++ b/terminal.c
@@ -1085,19 +1085,19 @@ static termline *lineptr(Terminal *term, int y, int lineno, int screen)
 
     /* We assume that we don't screw up and retrieve something out of range. */
     if (line == NULL) {
-	fatalbox("line==NULL in terminal.c\n"
-		 "lineno=%d y=%d w=%d h=%d\n"
-		 "count(scrollback=%p)=%d\n"
-		 "count(screen=%p)=%d\n"
-		 "count(alt=%p)=%d alt_sblines=%d\n"
-		 "whichtree=%p treeindex=%d\n\n"
-		 "Please contact <putty@projects.tartarus.org> "
-		 "and pass on the above information.",
-		 lineno, y, term->cols, term->rows,
-		 term->scrollback, count234(term->scrollback),
-		 term->screen, count234(term->screen),
-		 term->alt_screen, count234(term->alt_screen), term->alt_sblines,
-		 whichtree, treeindex);
+	modalfatalbox("line==NULL in terminal.c\n"
+                      "lineno=%d y=%d w=%d h=%d\n"
+                      "count(scrollback=%p)=%d\n"
+                      "count(screen=%p)=%d\n"
+                      "count(alt=%p)=%d alt_sblines=%d\n"
+                      "whichtree=%p treeindex=%d\n\n"
+                      "Please contact <putty@projects.tartarus.org> "
+                      "and pass on the above information.",
+                      lineno, y, term->cols, term->rows,
+                      term->scrollback, count234(term->scrollback),
+                      term->screen, count234(term->screen),
+                      term->alt_screen, count234(term->alt_screen),
+                      term->alt_sblines, whichtree, treeindex);
     }
     assert(line != NULL);
 
diff --git a/unix/gtkdlg.c b/unix/gtkdlg.c
index 9015dff3..5c69cb56 100644
--- a/unix/gtkdlg.c
+++ b/unix/gtkdlg.c
@@ -3705,18 +3705,6 @@ void nonfatal_message_box(void *window, const char *msg)
                 FALSE, &buttons_ok);
 }
 
-void fatalbox(const char *p, ...)
-{
-    va_list ap;
-    char *msg;
-    va_start(ap, p);
-    msg = dupvprintf(p, ap);
-    va_end(ap);
-    fatal_message_box(NULL, msg);
-    sfree(msg);
-    cleanup_exit(1);
-}
-
 void nonfatal(const char *p, ...)
 {
     va_list ap;
diff --git a/unix/uxpgnt.c b/unix/uxpgnt.c
index cb85b160..de990b93 100644
--- a/unix/uxpgnt.c
+++ b/unix/uxpgnt.c
@@ -23,16 +23,6 @@
 SockAddr unix_sock_addr(const char *path);
 Socket new_unix_listener(SockAddr listenaddr, Plug plug);
 
-void fatalbox(const char *p, ...)
-{
-    va_list ap;
-    fprintf(stderr, "FATAL ERROR: ");
-    va_start(ap, p);
-    vfprintf(stderr, p, ap);
-    va_end(ap);
-    fputc('\n', stderr);
-    exit(1);
-}
 void modalfatalbox(const char *p, ...)
 {
     va_list ap;
diff --git a/unix/uxplink.c b/unix/uxplink.c
index 2a1926ef..11ca7d1d 100644
--- a/unix/uxplink.c
+++ b/unix/uxplink.c
@@ -29,23 +29,6 @@ static void *logctx;
 
 static struct termios orig_termios;
 
-void fatalbox(const char *p, ...)
-{
-    struct termios cf;
-    va_list ap;
-    premsg(&cf);
-    fprintf(stderr, "FATAL ERROR: ");
-    va_start(ap, p);
-    vfprintf(stderr, p, ap);
-    va_end(ap);
-    fputc('\n', stderr);
-    postmsg(&cf);
-    if (logctx) {
-        log_free(logctx);
-        logctx = NULL;
-    }
-    cleanup_exit(1);
-}
 void modalfatalbox(const char *p, ...)
 {
     struct termios cf;
diff --git a/windows/window.c b/windows/window.c
index 88a29dd4..30cbbdc9 100644
--- a/windows/window.c
+++ b/windows/window.c
@@ -5522,23 +5522,6 @@ void optimised_move(void *frontend, int to, int from, int lines)
 }
 #endif
 
-/*
- * Print a message box and perform a fatal exit.
- */
-void fatalbox(const char *fmt, ...)
-{
-    va_list ap;
-    char *stuff, morestuff[100];
-
-    va_start(ap, fmt);
-    stuff = dupvprintf(fmt, ap);
-    va_end(ap);
-    sprintf(morestuff, "%.70s Fatal Error", appname);
-    MessageBox(hwnd, stuff, morestuff, MB_ICONERROR | MB_OK);
-    sfree(stuff);
-    cleanup_exit(1);
-}
-
 /*
  * Print a modal (Really Bad) message box and perform a fatal exit.
  */
diff --git a/windows/winnet.c b/windows/winnet.c
index 86f7735f..12fce5f9 100644
--- a/windows/winnet.c
+++ b/windows/winnet.c
@@ -257,7 +257,7 @@ void sk_init(void)
 	winsock_module = load_system32_dll("wsock32.dll");
     }
     if (!winsock_module)
-	fatalbox("Unable to load any WinSock library");
+	modalfatalbox("Unable to load any WinSock library");
 
 #ifndef NO_IPV6
     /* Check if we have getaddrinfo in Winsock */
@@ -348,7 +348,7 @@ void sk_init(void)
     if (!sk_startup(2,2) &&
 	!sk_startup(2,0) &&
 	!sk_startup(1,1)) {
-	fatalbox("Unable to initialise WinSock");
+	modalfatalbox("Unable to initialise WinSock");
     }
 
     sktree = newtree234(cmpfortree);
@@ -1529,26 +1529,20 @@ void try_send(Actual_Socket s)
 		 */
 		s->writable = FALSE;
 		return;
-	    } else if (nsent == 0 ||
-		       err == WSAECONNABORTED || err == WSAECONNRESET) {
+	    } else {
 		/*
-		 * If send() returns CONNABORTED or CONNRESET, we
-		 * unfortunately can't just call plug_closing(),
-		 * because it's quite likely that we're currently
-		 * _in_ a call from the code we'd be calling back
-		 * to, so we'd have to make half the SSH code
-		 * reentrant. Instead we flag a pending error on
-		 * the socket, to be dealt with (by calling
-		 * plug_closing()) at some suitable future moment.
+		 * If send() returns a socket error, we unfortunately
+		 * can't just call plug_closing(), because it's quite
+		 * likely that we're currently _in_ a call from the
+		 * code we'd be calling back to, so we'd have to make
+		 * half the SSH code reentrant. Instead we flag a
+		 * pending error on the socket, to be dealt with (by
+		 * calling plug_closing()) at some suitable future
+		 * moment.
 		 */
 		s->pending_error = err;
                 queue_toplevel_callback(socket_error_callback, s);
 		return;
-	    } else {
-		/* We're inside the Windows frontend here, so we know
-		 * that the frontend handle is unnecessary. */
-		logevent(NULL, winsock_error_string(err));
-		fatalbox("%s", winsock_error_string(err));
 	    }
 	} else {
 	    if (s->sending_oob) {
@@ -1738,12 +1732,8 @@ void select_result(WPARAM wParam, LPARAM lParam)
 	ret = p_recv(s->s, buf, sizeof(buf), MSG_OOB);
 	noise_ultralight(ret);
 	if (ret <= 0) {
-	    const char *str = (ret == 0 ? "Internal networking trouble" :
-			 winsock_error_string(p_WSAGetLastError()));
-	    /* We're inside the Windows frontend here, so we know
-	     * that the frontend handle is unnecessary. */
-	    logevent(NULL, str);
-	    fatalbox("%s", str);
+            int err = p_WSAGetLastError();
+	    plug_closing(s->plug, winsock_error_string(err), err, 0);
 	} else {
 	    plug_receive(s->plug, 2, buf, ret);
 	}
diff --git a/windows/winplink.c b/windows/winplink.c
index 84e47d6e..65dd7702 100644
--- a/windows/winplink.c
+++ b/windows/winplink.c
@@ -22,20 +22,6 @@ struct agent_callback {
     int len;
 };
 
-void fatalbox(const char *p, ...)
-{
-    va_list ap;
-    fprintf(stderr, "FATAL ERROR: ");
-    va_start(ap, p);
-    vfprintf(stderr, p, ap);
-    va_end(ap);
-    fputc('\n', stderr);
-    if (logctx) {
-        log_free(logctx);
-        logctx = NULL;
-    }
-    cleanup_exit(1);
-}
 void modalfatalbox(const char *p, ...)
 {
     va_list ap;