wow, that's really strange, wonder what causes this. So, as far as I got the problem, regardless of the version you're using, you always have the problem with flipping the sprites.
It's definitely not related to the amount of RAM you have, LF2 runs with 64MB (yes, our crappy school computers :P) as well as with 4GB. Maybe, some other applications interfere with LF2, you might want to check if there is any change when you disable some programs. Since I'm not familiar with 64-bit OS as well as Vista, I can't tell if this is related to the different architecture of the operating system. But because I've never heard any complaints from Vista-users, I can only hold the 64-bit-version responsible for your prob. I'm sorry but I can't really give you a 100% working guide to solve it. My only idea is: try 'n' see
@MH: dang, we both submitted in the same minute :P
edit by MH: and about same thing