first of all, thanks for winscp! Great product!
Now to my question:
When I'm connected to a host via putty and open a winscp session over a tunnel, I cannot use X11 any more
xterm Xt error: Can't open display: localhost:63.0
Once I close the winscp session, I can use X11 again. X11 tools started before the winscp-session are still usable - only the start of new x11-programs is affected.
Sometimes it helps to set the port to a fixed value instead of auto-mode but it's not a guarantee.
Not only that one SSH-Connection is affected by this problem but all (opened different putty sessions to different hosts) connections cannot start x11-progams as long as the winscp session is connected.
It does not matter which X11-Server is running (tried cygwin, vcxsrv, reflection-x).
It also seems to only affect X-Servers started for Display 0 (:0) ...starting an X-Server for :1 and setting up an ssh-session with display-location "localhost:1.0" lets me start x-programs on that server while the other session for :0 shows the problem (which goes away once the winscp-session terminates).