Sometimes you may get messages such as these at the console or in /var/log/messages:

Quota Error: kernel: VFS: Error -5 occured while creating quota.

This is typical if the quota isn't working right or is corrupted.

Perform these commands as root:

quotaoff -av
quotacheck -ugamn
quotaon -avug

If quotacheck segfaults or otherwise fails, you need to make sure quotas are off (quotaoff -a) and remove the quota files in / (for example, aquota.group and aquota.user) and then run quotacheck -ugamn again.