Yep, it's a filegroup/diskspace error and will be affecting all DB's on the primary filegroup (likely to be all of them) so your host will resolve it PDQ. Only thing to check is that you haven't got any outstanding transactions making your database large (ie 10Mb database and 138Mb transaction log!) - a full backup will cure this and truncate/shrink the T-log, but this won't make any difference if you've got 100+M of data in which case it looks like everything is fine, just run out of good old cheap disk :)
Thanks pdrq, I'm still awaiting a response from Pipex on checking if space is limited in any way and then to get it addressed. I'd have thought such an error would have ground everything to a halt but it seems sporadic, I've even deleted some 3month+ posts in one of the archived sections. Ho hum.
maybe it's sporadic due to the way the sql server is straining and occasionally committing large transactions which free up a bit of space in the meantime before it gets used up again - if the problems started rarely but increasing in severity that would be consistent