This is the second time I meet these difficulties. It happend after Winscp was working well for several sessions. But when this happens, the only way to get it to work is to complete uninstall it and re-install it afterwards. There is no crash and nothing specific I could tell you about strange circumstances before the misfunction. The only possible action in common between the two situations is that in both sessions I deleted files in the local default folder before closing the session. Before Winscp quits working (= not opening window after login) I was using sftp only. Now I am using scp only, so it should not be specific to a protocol.
This problem seems to be related to the one mentioned here https://winscp.net/forum/viewtopic.php?t=2134 ,
exept the fact that after a newinstall WinSCP works for several sessions.
I have no idea what further information I could give you to help you to locate the misfunction. I am now using v 375 beta, and I had in use the v 374 before. I am not sure whether or not the first misfunction happens with v374 or v375b.
system is winNT4.0 sp6a