[Dovecot] Failed to create storage with data - possible reasons?

Hi I'm getting this error with my attempt at setting up dovecot for virtual mail accounts:

Failed to create storage with data: /home/vhostpath/usersname/Maildir/

I cant establish any cause. I dont think its permissions as it was saying 'Permission denied' till I fixed that and the UID and GID are those of the directories owner. I was prompted bythe log files to set the minimum and maximum uid range, which made the prompt go away, but I still have this problem.

Can anyone tell me what else might cause this error?

Thanks glenn