Server Error After Upgrade to 5.2.1

Guys

Just done an upgrade to 5.2.1 and now my site returns a server error.

Can access admin no problem, can access everything until it requires clientarea.php?action then whamo...server error.

Any ideas boys?

Does this on both custom template AND standard template...

UPDATE:

Just rolled the clientarea.php back to 5.1.3 and now it is stuck in maintenance mode front end. Bit less embarrassing than a server error but never the less....ticket gone it now too.

Thanks
Daren