This Happens to me before after that all program that runs under The old WinCE Won't run (like the PalmGB). Then When I was installing a Game I accidentlly overwrite the old GX.DLL file under Windows Directory, after that I was able to play MameBOY again. I think just by trying to re-install the GX.DLL again will get rid of that error message. Try it and see if it works.