[OM] stuck filter on 49-72 step up ring

[NSURIT]

I know we beat the stuck filter question to death a few months ago, however I 
think my stuck filter problem may be a bit unique.  What is stuck on the step 
up ring is a B+W slim circular polarizer.  What I need to grip is the back 
part of the filter and I'm having a heck of a time trying to get it to move.  
Any ideas that won't destroy either the ring or the filter?  Bill Barber