[crunch]

I guess it depends on your game settings, but I
NEVER use Alpha channels, and it always works. In fact, it works ONLY with NO alpha channels.
I also never size it to 512x512. I always use 800x600 because that is the size of the border (unless of course you edit origin locations in the .urc file), and your image won't get cut off or stretched that way.
Doing it this way, I have yet to run into any kind of trouble.