this seems to happen all the time. i get an email saying that the advertiser is deactivated and then either the same or next day that they are reactivated. anybody know why?

Advertiser have to renew thier membership
so when it expire it deactivated
so they renew it and it activated
well as far as i know

Only some advertisers have to renew their memberships (or refill their accounts), usually the smaller ones. Those are the ones that you'll see deactivate/reactivate.
Most of the big names are auto-activated.
I've had small guys deactivated and then six months later they'd pop up again. Of course I'd moved on but it was funny to see them trying to pay the bill and get back in CJ's good graces.

I also suspect it has to do with them paying their bill a few days late as well.

If advertiser funds are finished in their accounts CJ makes them deactivate. If they deposit money again then it becomes activated again.