Why is my iPhone not recognized on my USB port?

Question

When I try to connect my iPhone 3G to my computer absolutley NOTHING happens. No error message no beeping from windows that it detects a connection, and I definitely cannot see it in my iTunes. I have tried restarting the phone, resetting the phone, restarting the computer, restarting the computer with my phone connected, reinstalling iTunes/Quicktime, plugging the cord into different ports on my computer (not my keyboard) and still nothing. I have an external drive with a USB port connection that is recognized when I plug it in the same USB ports. One would think it was the USB cord but the strange thing is I can use the same USB cord plugged into my phone and the adapter in the wall and it charges. I just can't update the software or add songs to my iPhone.
Anybody know what's going on?

Answer 1

Ok so I tried creating a new user account with administrative priviledges on the same computer and still nothing. I called apple tech support and spent about an hour on the phone with them and they are baffled as to why this is happening too. Their only suggestion was to replace the phone. So unless someone else has had this same problem and knows hows to fix it, or just knows of something that apple doesn't, I'm screwed!
Just out of curiosity, I tried connecting my phone to another computer to get the 2.2 update and it worked. So I updated my phone's software and tried plugging it in again and still nothing. Also, I tried connecting someone elses iPhone 3G to my computer with the same USB cord and my computer recognized their phone. So it must just be my phone and my computer don't like each other for some reason!
Here's the full scenario before the connection issue (just in case someone knows something I don't):
I was having problems updating my iTunes to version 8.0.2. It wouldn't fully install quicktime and without quicktime you can't run iTunes, in fact, iTunes won't even open. I got an error message that said I needed to repair or reinstall quicktime. So I completely deleted iTunes and quicktime software from my computer and reinstalled the version that is downloadable from apple's website (which is NOT 8.0.2). I got it loaded and alas iTunes finally opened. So I connected my phone and started updating to the 2.2 version of iPhone software. Then a window popped up saying I needed iTunes version 8.0.2. So I started that download as well. Then I walked away to let it download the updates needed for my phone and iTunes. I came back 20 min later and my computer had restarted itself (I'm assuming after the iTunes update it did that) and was at the login screen. So I logged in and my iPhone would then not connect to my computer after that. I unplugged and plugged it back in and I got a beeping noise but not the normal beeping noise a computer makes when you connect the USB cable. It beeped three times in the same lower tone instead of the 2 beep 2 tone you normally get. I realize in hind site that was probably not a good idea but I asked the apple tech I talked to and he said that shouldn't have been a problem even if the 2.2 iPhone update hadn't fully installed and had been interrupted. So there's my full story! Thanks for helping me out!!