Sorry Martin, it looks like this bug had been fixed in a later version (I updated to 5.1.7). Silly me, I didn't update WinSCP [Talking about which, you might want to consider an automatic update solution, or at least download and launch the installer right from the 'Check for updates' function.]
I'm not a 100% sure it's fixed, but if I get it again, I'll report it (after updating and reproducing the error :) ).
I'm not a 100% sure it's fixed, but if I get it again, I'll report it (after updating and reproducing the error :) ).