Lots of database errors

[Floyd R Turbo]

I have been running VB4.2P2 on GoDaddy hosting for a few months. I also use vb Bad Behaviour and GlowHost Spam-o-matic and it seems to do a good job so these might be related to that security in place. But i just wanted to check because I keep getting this error message:

Database error in vBulletin 4.2.0:

Invalid SQL:
SHOW COLUMNS FROM user LIKE 'username';

MySQL Error   : Incorrect key file for table '/tmp/mysqltmp/#sql_XXXX_0.MYI'; try to repair it
Error Number  : 126
Request Date  : Wednesday, March 13th 2013 @ 09:19:55 AM
Error Date    : Wednesday, March 13th 2013 @ 09:20:05 AM
Script        : http://www.turbosaquatics.com/vb4/register.php?do=addmember
Referrer      : https://www.turbosaquatics.com/vb4/register.php
IP Address    :  [varies]
Username      :  [varies]
Classname     : vB_Database
MySQL Version :

the XXXX_0.MYI has been one of 2 numbers.
The IP Addresses are always different
The Usernames are always ones that are not registered.

So is this just automated spammer activity I am seeing, and their attempts to post something without having registered is causing a database error e-mail to be generated?

This is not the only recurring error I am getting, but it is the dominant one. So I'll just leave it at this one for now. Thanks

--------------- Added [DATE]1363637302[/DATE] at [TIME]1363637302[/TIME] ---------------

Correction I'm running PL3

also I'm running GlowHost SOM 2.0.2