Okay, I suspect diagnosing the problem would take forever with my limited knowledge and ability to explain.
I've copied and pasted all the stem files to a fresh, empty Logic file and now can pan my vocal tracks.
I need a simple instruction sequence for creating a vocal track stack and adding reverb to each vocal track as needed. The key is simplicity - I can barely understand Logic's bussing layout!
Also, any simple do's and dont's list to keep latency from becoming a problem would be great - things like sample rate and other settings in preferences.
Thanks
Ritchie