When searching the moderator logs for anything that ends with ) or ( causes the following PHP notice to be shown multiple times:

[phpBB Debug] PHP Notice: in file /includes/functions_admin.php on line 2566: preg_match() [function.preg-match]: No ending delimiter '#' found

Here are some of the search terms I've used to trigger the notice

foo)

foo(

foo (bar)

I found this on phpbb.com and other team members on IRC reproduced this bug on 3.0.6-RC3

The notices don't show up if you add a # at the end so "foo(bar)#"