WinScp (<= 4.2.1) work very unstable with ftp-servers on bad connections. If "ping" server at this moments, we have "Request timed out". At this moment if WinScp tried upload new modification of file (external editor), or update directory listing, it "Not Responding" until user not close it.
Not tested other type of connections. Only simple FTP.
Can you send me an email, so I can send you back a debug version of WinSCP to track the problem? You will find my address (if you log in) in my forum profile. Please include link back to this topic. Thanks.