I think we're experienceing this very problem..
WinSCP logs on, then the interface disappears. Taskmgr shows Winscp process still running.
And now for the weird part. When you run procmon (from sysinternals.com) and have it capture events, Winscp will behave as expected.
When procmon is stopped (capturing events)/exited Winscp will revert to the crashing behaviour..
This occurs on WinXP SP3 with WinSCP 5.06 (build 2074) and Process Monitor v3.0
Hope there's a solution to this as havving procmon running slows down the system significantly.
Thanks for your report.
I have sent you an email with a debug version of WinSCP to address you have used to register on this forum.