i would think that you should clear your cache in E and the Z,Y,and X partitions. that should work. if not, you may need a new drive. if your failing the stock maps, something is wrong with your drive, it happens to my thompson all the time, so you may need to get a new laser of a new drive entirely. if you failing the new content, their may be a couple of things wrong.
A. try clearing the CACHE
B. if you fail the maps on the drive, something has to be wrong how you got them. did you be a pirate and dl them off of bt? or did you get them from live directly? if you get them from live directly, there should be no problem.
C. i know this is a stupid question, i know it, but did you really download the ones that people are playing? if you dont have them, it will give a failed message.
Good luck, becuase the maps add so much more to the game, so i hope you get it to work.