Aperature problems with 20D & 17-85 EFS lens

I purchased a 20D a couple of months ago and am really starting to get into the "guts" of its potentials.

I'm using the 17-85 lens that came with the package.
Question: In manual mode, I can adjust the shutter speed to whatever I want, but I am not able to adjust the aperature. If I go to aperature priority, then I can adjust the aperature. BUT, according the the manual and common sense, should I not be able to adjust the shutter speed AND aperature in manual mode?

Is this user error, a lens issue, or something else? Thanks to everyone!

On the back of your camera, look at the on/off switch, it has a third position, right above on, it's just a bent line. Turn your power switch to that position and thenm in manual mode, the quick control wheel (the big one next to the power switch) will set your apature. (page 16 and page 80 in your manual).

I've only had my camera for 5 days now so I'm learning it too Maybe somebody can explain why there are two on positions.

Doesn't the manual explain the two on position are for?
I guess I'll find out when my comes in a week.

Tried that. Still, I can only adjust the shutter, nothing with the aperature, it stays fixed at 6.7. I'm wondering if I need to send it in?

Are adjusting via the wheel next to the LCD?

Adjusting both small wheel on top and big wheel on back. Small on top does the shutter speed, big one on back does nothing.

If it's in Manual, the "on" switch should be pushed up one more notch to the bent line.... then the big wheel in the back should change the aperature. If it doesn't, did you try taking your lens off, take the battery out, and starting all over again?

If that doesn't work, did you play with any of your custom settings?

If not... sounds like you need to have a camera guy look at it.... that doesn't sound normal at all. Sorry.... hope it's only the on switch thingy!

Just out of curiosity..... what is your lens set at (I mean, what mm setting)? Not that it should matter, but are you trying to go below 6.5? You did try turning the big wheel in the other direction... correct?

Yep, have tried everything as described in this thread....I've even updated firmware ('cause of my 430 EX flash) hoping that might do something. I guess I run it down to a local camera shop. Then see what happens.

Good News! I reset ALL CAMERA SETTINGS and it looks like we're up and running. Hopefully I can figure out if there was a setting somewhere that I changed that I can pass on to others that might end up with the same problem.

It really made no sense to me. But I can again change both aperature and shutterspeed. Thanks to all.

Told ya! At least it works now.... have fun...

Nobody answered the question about the on switch having 2 settings.

I've read the manual and can't find anything about it. Just that 'on' is at the line, (second setting).

Page 26...
Also mentioned on page 28

I think it is so that you can 'lock' the wheel on the back so you don't accidentally move settings ( a hazard for people like me with large noses...)

I think I answered the wrong question... (doh!)
I know with my 10D I was forever catching the rear dial, so the option to turn it off helps. Also with my 10D round my next the switch would often be caught and turned off... the 20D switch improves on that too.