Why does du and quota results not match?

I have exceeded my disk quota on a system which I do not have root access. I tried removing old files but am still over. I tried runing du to find where I am using up all my space but it reports I am using very little. Results from quota /home/1234$ quota -s Disk quotas for user 1234 (uid 1234): Filesystem space quota limit grace files quota limit grace cslab:/home 4519M* 4096M 5120M 09:47 6155 0 0 From du /home/1234$ du -mad 1 ... 936 total I don't understand why quota says I am using 4.5GB while du only counts .9GB. I also checked for files I own in /tmp and there was 50MB worth of files there. *Where could the other 3.5GB of files be? Is it possible the quota system is wrong and needs reset?*