Thank you very much! You solved my problem. Except that I had installed the Rev.E firmware when I should have installed the older Rev.D firmware. Problem solved.

I have been successfully printing for the past few weeks and decided to upgrade to the 2 nozzle extruder. Finished installing new parts, and attempting to re-level M2. Whenever the bed rises to the z stop the bed drops back to the bottom and tries to go up to the z stop again, at which time it reset...