carving bit plunges into the wood, then homes.

I just received my machine back from mantenance, carved one project successfully and on the second project the following happened.

The carving started and made about two passes, when the bit plunged into the wood and and the bit carved directly to the home position at the depth selected for the project. I tried it again after powering down and the same thing happened.

If anyone has had a similar problem please let me know as I have some commitments to meet. Thanks Dan