Mike -
I know you from the other board - on Gardenweb......
I'll bet you anything its the fact that your PH is too high. Our SWG did the same thing....stopped producing chlorine due to the PH being too high., so now we make sure we keep our PH in check.
You need acid to bring your PH down.......most positively your answer.

Let us know if that worked.
Shari