Disk Quota not enabling

Folks,

We're having a problem with enabling quotas on our client accounts.

I've set everyone's account limit in workgroup manager, then under server admin i've ticked the box to enable quotas, but it won't save.

At first, this didn't seem to be a problem as we have 4TB available to share to the clients. However, it's becoming clear that the students cannot be trusted with this amount of space and are downloading torrents left right and centre. So we really need to restrict their accounts again.

Can anyone give me a clue as to what we can try? I was thinking of stopping all services on the server, then enabling quotas, then restarting all the services. Just to see if this would work?

Failing that - it's a complete wipe and rebuild in the summer.

Cheers

Dan