Can't run files on mac filesystem in windows

This is a really weird problem that revealed itself within the past two months: I can open up the Mac drive -- I can even see icon previews, but if I try to run the file directly off the mac drive, it fails; I always get some weird error message from the program, whether it bee VLC, Quicktime, WMP, Windows Photo Viewer, etc. In order to use these files, I have to copy them to the Windows partition first -- which is REALLY annoying to do EVERY DARN TIME.

HELP!!!!

P.S. I'm using Windows 7 64-bit ultimate if it makes any difference.