I'm working with another artists's file, and I can't seem to release the clipping mask he created. When I try, I get an error message that says, "Can't ungroup the objects." I've tried releasing Compound Paths, but I get the same message.
See if you can isolate the object(s) and check if they are all on the same layer. It may require a process of elimination to see how the pieces interact with eachother. I sense it is a layering problem.