Check out this video clip:
Beretta Model 21A Bobcat (22lr) : Overview - Disassembly - Cleaning - Reassembly - YouTube (start at 1:40 mark for slide removal)
and go read this thread:
Beretta Model 21A Disassembly Problem - The Firing Line Forums (post #6)
for details on what else might be causing problems.
Hope this is helpful.
Those are nice little guns. I had one many years ago, but I traded it off in a moment of weakness. I kind of miss it.