I had a similar problem that I got help with here. (Thanks everybody).
http://www.cnczone.com/forums/showthread.php?t=74699 (0m not ready)
I was able to get my machine to move by HOLDING in the machine end release button. The problem I had was a broken wire at the connector for the limit switch. you may want to read the other post, as they also gave other possibilities to check before I found my problem.