Shutdown p5000etch SNF 2007-12-06 12:18:45: Wafer stuck in chamber C

I was etching 4 wafers in chamber C. 2 wafers etched without problem, but the third wafer did not come out of Chamber C. I got an error message "Cannot close I/O slit valve, blade may be in it." The blade is not stuck in the slit so it must be another problem. I tried to "Home all robot axes" but it could not recover the 3rd wafer.