I don't know if anyone asked this question.

Since my Xbox 360 joined Live, and I started downloading demos, I found when the 20GB hard drive has about 3.5GB disk space left, each download will fail. Even game update and games can't write to the hard drive. The hard drive behaves like it's not writable. Whenever I deleted a demo up to about 3.8GB disk space free, download, game update and game save will work again. I hope hard drive isn't corrupted because I hate having to download everything again, plus I don't have any memory card space to transfer all the saved games.

I already tried Y+X,X,LB,RB,XX to clear the cache but as long the hard drive has about 3.5GB of disk space left, it wouldn't anything write to the hard drive.

I have been playing on my Xbox for 11 months without joining Live, and never had problem with saving games to the hard drive. This problem started after I started downloading a lot of demos.

Has anyone seen this problem?

i'm not sure.. but i have a feeling this might be reserved space for game caching.

I have had my hard drive down to less than a GB free so I think something might be wrong with your drive. There is already space reserved for caching that is part of the 7GBs that are always taken up when you try to delete everything off the drive.