There is a problem with the front focusing on the 20D, and I suspect it is a lot more common than many people think. I had a 20D until a few weeks ago, but it was suffering the same. After looking at a few in my local shop, there were all showing the same problem.
My supplier somehow managed to strike a deal with Canon whereby they exchanged the unit for a 1D MKII. A shame because I really liked the 20D.
Like previously said, in the mass production market, I would imagine that if a fault exists it gets passed down the line to many units.
It might be a good idea if you contact some of the photography magazines about this. If they do a write up on it, Canon may feel obliged to look into this problem properly, and if needed issue a product recall for affected serial numbers............................................but then again it might not