err 99 using 20d with tokina atx 28-80 2.8

i have problem using the 28-80 atx tokina lens with my eos 20d.
any ideas??
anyone with the same problem??

Err99 is a catch-all. It could be something as simple as the lens and body's contacts not making contact. With older Sigma lenses, it could be that they need re-chipping, since Sigma had trouble successfully reverse-engineering Canon's EF electronics; I haven't heard of that happening with Tokina lenses, but that's not one we see mentioned a lot around here.

I had intermittent ERR99's with my 350D and Tokina 12-24. I read in a thread here that the aperture blades sometime need "working in". Try setting the aperture to f22 (or max stoppep down) and firing off a hundred "blank" shots. Worked for me.

I have experienced this a few times with my 20D. Each time I took the battery out waited a few seconds and reinstalled and it cleared it. The last couple was with my canon 70-200 IS lens on. A friend has the rebel 300D and when he attached his older canon lens it locked in err99 . it was fixed only by replacing the small battery. In the Book it says to remove the battery and check all connections.