Digimage - I know what you mean. I've seen this on other cans of solvents and they're a real pain. The seal should have a very tiny, thin, lip around the edge. Try to pry under this and raise it enough to get a bite with a pair of pliers, then put on your safety glasses, hold the can down really well, and pull off the seal. If this doesn't work, just punch through the seal with a small screwdriver and pry it off. Which ever way, though, make sure you cover your eyes. When it comes off it can flip some of the contents right toward your face.
Good luck and let us know if that works.
Stinger