Well it's something new with your recent updates. I ran one of your previous releases of the RPG system just fine (I think it was 2.9 or something).
I'd just really hate to have to wait that long without it.
----Edit----
Another problem I didn't mention earlier was rpg_install.php got this error upon running the installer.
Code:
Invalid SQL: UPDATE `rpg_class` SET `type` = '1'
mysql error: Table '(database name).rpg_class' doesn't exist
mysql error number: 1146...
I wasn't aware rpg_class was supposed to be present...