Your monitor driver for some case forbid you using the specified refresh.
If your card is ATI, then seek the damn option and uncheck the "use DDC informations" :?
If your card is nVidia, things should work, unless you use any obsolete version fo Detonators - in this case, please update your drivers
PS. what about to use just your desktop resolution w/o any changes for fullscreen mode? It always worked well for me...
Delete the BSplayer prefs and try again. I have the same Win2k SP3 and latest version (as all the previous ones) worked for me flawlessly - except one pause/play AC3 glitch... :oops: