Problem with new registration

[Correadde]

For some reason some visitors have problem register with my site. They will get the error message saying the username they chose is not available, I check the database and that name isn't in use. What might cause the error message? They try to delete cookie, cache and still having the same problem. I get this error:



Database error in vBulletin 3.6.5:

Invalid SQL:
SELECT id,name FROM file_cats ORDER BY `order`;

MySQL Error : Table 'Andreas_xxxxx.file_cats' doesn't exist
Error Number : 1146
Date : Saturday, May 19th 2007 @ 09:14:18 AM
Script : http://vagklubben.se/forum/cron.php\?&rand=661131
Referrer : http://vagklubben.se/forum/private.p...der&folderid=0
IP Address : xx.xxxx.xxx.xx
Username : Oregistrerade
Classname : vb_database
)

What can the problem be