So, I still use my trusty old Canon 20D, long in the tooth but has always been reliable and as I'm not a pro I never felt the need to replace it, my daughter has shot a lot of weddings with it and every customer has been well satisfied.

Anyhow, crux of the buiscit is this; I have been using a Canon zoom, 70-210 I believe but am to lazy to go check at the moment?? It has an ultrasonic focusing motor and has image stabilizer. I have been using it for about 4 months along with a couple kit lenses and have had no issues, until last weekend. I was at my sons for my granddaughters birthday and switched to my 18-55 knock around lens and it would not focus, no confirmation beeps or lights on manual, no display for focus mode, nada, nada, nada. Switched to another lens and same deal. I could manually focus and shoot but the camera was not recognizing either lens as AF, switch back to the 70-210 and everything works perfectly fine and I can chose focus mode in typical fashion.

Before anyone asks I tried all three lenses on my brothers 30D and they functioned normally, so I flashed the firmware on the 20D and it still won't recognise the focus features on the two smaller lenses. So what could be wrong and how do I fix it?

 
If a good cleaning of the contacts doesn't work and you've already removed and reinstalled the battery, then I think it's time for a new camera. You can get a nice used 20D for next to nothing these days. I would considder upgrading to a 30 or even 40D. They're a big jump from a 20D and around $150 tops.

Any resolution to this? My 40D has a similar issue which developed in the last week or so.