Summary:
The "Logout" link on the main page would return a session verification error when clicked.
The Shoutbox wouldnt allow submissions directly from the main page returning the same session verification error.
Cause:
Server Side:
The way Joomla 1.5 and SMF handle sessions are not directly compatible. Each tries to save its own sessions seperately however Joomla was killing the SMF sessions to make room for its own.
Fix:
PHP code had to be adjusted to compensate for the killing of session ID's. New code has been implemented and both functions now work properly on the main site.
Huge thanks to Koth for fixing this.