This is a bug in 5.5 and it is fixed with 5.6.
To stop getting this error I just sent the warning to /dev/null to ignore it as I do not use quota's in any way, shape or form, but this might not be suitable for everyone.
Take a look through the bugs section of e-smith.org or do a search for this here and you will find numerous people with the same problem.
Cyrus Bharda