Did you break the Red Lock Tab on the Upper Right, or the Black Release Tab just above my thumb?
The Red Tab is the Lock Tab. You'd have to Unlock this first. If it's NOT
the one broken, just slide it about 1/16th of an inch to the right, until you hear a click. Now, if the Black Release Tab is indeed the one you broke, do as InfernoGirl mentioned, and try a screwdriver, and press down where the Black Release Tab would have been.
Let us know how things work out!
Best of Luck!