I'll chime in: If the inside rear wheel is actually leaving the ground, as said check and make sure the rear suspension is moving freely. Insufficient drop would lift the rear wheel. Are the rear dampers adjustable and if so do you have the rebound set uber stiff? Per Carroll Smith's books work on the end that is a problem first. It sounds as you may have someone to help you check it out, I would recommend that. Also can you tell us if the car has snap oversteer etc. Basically something is reeeeeally out of whack, I've seen/experienced a few 1200's lifting the front and even both inside wheels at once (I found it sort of entertaining) but never the rear only.

Tom