Avid has some strict requirements for graphics cards with MC 3+. They are all in the nVidia Quadro FX line of cards.
With that said I am not 100% certain if this is your issue. If you have another machine that is using these same graphics and you are running the same graphics card/driver combination then you probably have a different issue.
If it is working on other machines I would verify if the specs of those machines match this one.
One thing you could possible try is rebuilding the database files for your media.
If you know where your media is located on your internal navigate to the folder (OMFI MediaFile or Avid MediaFiles)and delete the two files named msmMMOB.mdb and msmFMID.pmr.
When you relaunch Avid the media folder will be scanned and it will rebuild the files and/or find corrupt media files. If it finds corrupt media files you may need to recapture or reimport the materials that are corrupt.
-Matt