I found this information on the web.
If your Xbox is freezing or slowing down, clearing the memory cache can help improve its efficiency.
"To clear your Xbox 360 memory cache, do the following: go to the "System" blade and select your console's hard drive. With the hard drive selected, input the following buttons: Y, X, X, LB, RB, X, X. A message will appear asking you if you wish to perform maintenance on your Xbox 360 storage devices. Select "Yes," and within a few moments your Xbox 360 hard drive will clear its memory cache. Keep in mind that clearing the memory cache will remove all software updates that you may have downloaded for other games, so you'll need to go and download the updates again." - Gamepro.
Just thought I would post this because a few people have been saying their Xbox's have been freezing.
Tattie