You're probably better positioned than we to know whether the BB has a square shaft. You should be able to see it without even removing the cranks.
As for a replacement if it does, you might consider the older Shimano Deore LX cranks. I'm not sure whether the newer version has removable rings. There are several older sets on ebay as this is written.
P.S. You do know that left pedals are reverse-threaded, I assume? If that's the one that is giving you problems, are you turning it the right direction?
Last edited by GCRyder; 10-11-06 at 02:43 PM.