Sorry that you've been having so much trouble with your USB port. There are issues with the PDIM where it will periodically not respond to messages from the radio which is when you will not see the Aux jack when pressing the CD/AUX button. This issue should be resolved with a software update coming at the end of July. I'll post a message when the update is available. I don't think it's a matter of connection or the iPod that you're using as I've heard of this from multiple people.
I have a 2LT 2010 Camaro purchased Jan 2010. The Auxiliary In / Out worked great with the 5th gen iPod until around Easter. Something happened and the car could not see these two devices. I took the car to the dealership to get this fixed June 4th and they found a loose connection at circuit X302. The ports were visible again and I started using the iPod. This fix did not last long, the first time that I unplugged the device the Aux ports were not recognized again. The dealer ordered a new harness (92205058) and receptacle (20870101). This was installed and the fix lasted for two days. The AUX ports are not recognized when the CD/AUX button is pushed. I haven't read any posts like this one, but I'm still searching. Do you have any ideas? Is the problem with the iPod? Any advice would be greatly appreciated.