DB Error? Help please.

[KDawg08]

Database error in vBulletin 3.8.4:

Invalid SQL:
SELECT COUNT(DISTINCT(userid)) AS count FROM session WHERE session.userid>0 AND session.lastactivity>1271479245;

MySQL Error : Out of memory (Needed 1048548 bytes)
Error Number : 5
Request Date : Saturday, April 17th 2010 @ 01:10:45 AM
Error Date : Saturday, April 17th 2010 @ 01:10:47 AM
Script : http://MYSITELINK.net/misc.php?show=ccbmessages
Referrer : http://MYSITELINK.net/index.php
User : Justin

How do I fix this? LOL... I am getting TONS of emails saying this... Any suggestions?
This is happening with more than one user: showing up. for example Justin, -Noodle Squad- etc.



here is the recent info from my error log file:

[13-Apr-2010 04:05:16] PHP Fatal error: Out of memory (allocated 6291456) (tried to allocate 19456 bytes) in /home/twistede/public_html/includes/functions_user.php on line 677
[13-Apr-2010 04:05:16] PHP Fatal error: Out of memory (allocated 6553600) (tried to allocate 311296 bytes) in /home/twistede/public_html/infernoshout/engine/inferno_shout.php on line 491
[13-Apr-2010 04:05:16] PHP Fatal error: Out of memory (allocated 2621440) (tried to allocate 16 bytes) in /home/twistede/public_html/includes/class_core.php on line 1335
[13-Apr-2010 14:51:09] PHP Fatal error: Out of memory (allocated 786432) (tried to allocate 311296 bytes) in /home/twistede/public_html/includes/init.php on line 505
[15-Apr-2010 19:29:46] PHP Fatal error: Out of memory (allocated 5242880) (tried to allocate 57 bytes) in /home/twistede/public_html/includes/functions.php on line 5266
[16-Apr-2010 05:00:21] PHP Fatal error: Out of memory (allocated 6291456) (tried to allocate 311296 bytes) in /home/twistede/public_html/global.php(607) : eval()'d code on line 322