Problem p5000etch SNF 2008-07-06 15:17:58: wafer is stuck in Chamber A

My Wafer is stuck in Chamber A
I used CH.A METAL TIMED recipe to etch Al.
"Wafer did not drop in blade from Chamber A"
I have seen this error message 3 times this week.
Please let me if there is problem in using Chamber A or the way to solve this problem manually when I see this error again.