Dear Angus,
there is a small bug in os_win32.C (tested with LyX 1.3.6cvs):
Function "cygwin_path_fix(bool)" must be part of namespace "os". Please change the signature to "os::cygwin_path_fix(bool)".
Thanks, Michael. I've just spotted this myself.
Incidentally, apart from the fact that the graphics conversion (for the screen) blocks the execution of LyX, I think that LyX 1.3.x/Win should now be a fully-functioning equivalent of LyX/*nix. If you really are using it in anger, then I'm sure that you'll discover bugs. Please report 'em all.
Thanks, Michael
Angus