Graziano SAG 210 Lead screw turns But carriage Doesn't feed.

Doing a rush job over the weekend on my Graziano SAG 210, and feeding along nicely, and all of a sudden the feed seems to overload, and I hear a crack. The feed screw is still turning, but the carriage has stopped moving. It won't feed manually.

I'm looking through the manual to see if I can find what may have popped before I rip it open. I can't seem to see what would be gone. The pinion in the back won't turn when I spin the handle as if feeding manually, but I can see it rock back and forth as I change direction with the handle.

Can any one help?

Cheers