Hi everyone,
I am encountering a similar problem forums/forum.php. It seems only forum.php is affected.
This is what is displayed
"DzPhoeniX Here :P | PS :: Don't Mind Just kidding

"
Other pages are fine.
If I log in as administrator, forum.php loads correctly.
After some investigations in the admin logs, I found admin users created and logs show this:
I have already disabled those accounts but would like to know how to resolve the issue other than a database restore. It seems there could be a plugin or a template edit.
A search for "DzPhoenix" in templates led me to FORUMHOME which was blank except for the line above. I thus restored FORUMHOME back to its original state and everything seems fine again.
Is there anything else I should check on? I'm a bit worried about the references to plugins above and would appreciate any help on this.