I had the same problem a few weeks ago when our pool was opened, you can see the post http://www.poolforum.com/pf2/showthread.php?t=1260

Mine was only a couple of seasons old, and I ended up buying a replacement cell. Everything is working fine now. Unfortunately, I had to partially drain and refill becuase I added too much salt.

I would try cleaning the cell first (I did it three times even though it looked clean).

Kevin