I know, I know, I might be the only person on the planet with this problem, and my guess is that it's not a WinSCP plugin issue, nevertheless I thought I should inform you.
Thing is, I use FAR 1.70 (build 2087) with WinSCP plugin 1.6 beta and ConMan 2.35. When I use it on 32-bit XP it works fine, on Vista Business x64, however, it crashes whenever I press F4 on any file. Without either conman or WinSCP this bug doesn't present itself, I just can't have them both. It seems to me that ConMan and WinSCP don't like each other under Vista x64 (dunno about x86).
Things don't look bright for me if this is a ConMan bug, as ConMan doesn't seem to be alive anymore, last version is from 2005. Even though it's old, it's a very useful plugin, I don't think I could return to plain FAR anymore.
I'm sure you've got better things to do, but any chance of you looking into the matter?