[cbj4074]

The solution to this problem is as described at http://forums.debian.net/viewtopic.php?f=5&t=59985 .

# modprobe quota_v2

Check if the module was loaded (no point in proceeding if not):

# lsmod | grep quota
quota_v2               13402  2
quota_tree             18351  1 quota_v2

Add quota to module configuration:

# echo 'quota_v2' >> /etc/modules

Delete the files created previously (/aquota.group and /aquota.user ):

# rm /aquota.user /aquota.group

(The next command will re-create those files with the correct permissions and ownership.)

Check quotas:

# quotacheck -avugm

Enable quotas:

# quotaon -avug

Thanks to http://forums.debian.net user "pabloncho" for the solution!