How to fix this database error?

[MarkFoster]

This is the error I get:
Database error in vBulletin 3.8.6:

Invalid SQL:
SHOW COLUMNS FROM userfield LIKE 'field0';

MySQL Error : Got error 28 from storage engine
Error Number : 1030
Request Date : Tuesday, March 22nd 2011 @ 02:43:43 AM
Error Date : Tuesday, March 22nd 2011 @ 02:43:43 AM
Script : http://www.xxxxxxx.com/forums/showthread.php?t=3740
Referrer :
IP Address : xxxxxxxx
Username : Unregistered
Classname : vB_Database
MySQL Version :

I get it occasionally for 0-4 hours. I have no clue how to fix it.

[Lynne]

One or more partitions on your server is out of space or doesn't have enough space to complete this operation. You need to shutdown your forums and contact your host immediately. You or your host will need to find out which partition is low on disk space and either add more space or free up some.

[harisafp]

low space server ...
or optimization your forums first.
like this threads (http://hitech-forums.com/vbb/showthread.php?t=14137) ... !
ThQ.