Playback is greyed out for dvds on media player classic

every dvd i playback using media player classic 6.9.1 is greyed out...meaning i can see the video images but they are as-described greyed over...i have no idea what could be causing the problem. Im using a dell inspiron 1420 with windows vista

DVD-Video is a separately licensed codec I'm not familiar with your player, but "Windows Media Player" will not play DVD-Video without installing the proper codec.
Somebody may know of one you can download and install for free. Otherwise you can track one down through Microsoft or consider an aftermarket, paid program, such as Nero, PowerDVD, or WinDVD. Most media creation (burning) suites come with a player Nero in particular has "Showtime".

If your player has played DVD in the past, you might consider the possibility that the program and/or it's companion codec has become corrupted and needs to be un-installed then re-installed.