Wow, it seems this is happenin all to often! We are going through the same by the sounds of it.

I would recommend putting everything in writing to your boss to at least give him the chance to rectify the problem and ask for all correspondence to be in writing, that way you will have all your proof.

If you get no joy you can put a greavence in against him, that should do the trick.

I wish you good luck :-)