Classes not available for tasks?

[Mike Pokraka]

Hello list, 

I have two systems, both 620 patch 54, however on one system I cannot create
tasks based on classes - only Business Objects is available from the Object
Category drop down. The other one lets me use CL and BO's. 

I've been through config and help and can't find anything on how to enable
classes. 

Any hints appreciated, 
Cheers
Mike