I just ran "quotacheck -acguvm" and got the following output:
[[email protected] ~]# /sbin/quotacheck -acguvm
quotacheck: Scanning /dev/hda6 [/home] quotacheck: Old group file not found. Usage will not be substracted.
quotacheck: Checked 6 directories and 13 files
quotacheck: Can't create new quotafile /home/quota.user.new: Read-only file system
quotacheck: Cannot initialize IO on new quotafile: Read-only file system
The thing that's confusing me is at some stage /home seems to be setting itself to read-only, but unmounting and remounting the drive fixes this back to the normal read, write and execute.