Cannot See Nano in Device Manager, ITunes or Ipod Updater

Help! I purchased a new Nano 3 weeks ago and I have been struggling with it ever since. I had it working very briefly, with some songs loaded. However, I then applied the lastest update (03-23) and my nano hasn't worked since. I've tried everything. I've uninstalled and reinstalled. The Nano does not show up in Windows Device Manager, and it does not show up in Itunes or in ipod Updater. In all the postings I've read with suggested solutions the nano was at least showing up SOMEWHERE. Mine doesn't show up in any of the three places. The songs I had loaded onto the Ipod disappeared, although they still show on my computer in ITunes. I have 2 USB 2.0 ports, and I've tried switching between those, but that still doesn't work. I am able to plug my Palm into either of the 2 ports and do a Hotsync, so I know the ports themselves do work. One post suggested putting the nano into disk mode before opening up the ipod updater. I have tried and tried to get my nano into disk mode and I can't get it to do that. The Apple logo comes up, I try to press Select and Play/Pause but it just comes up with the language selection list. I click on "English" and it brings up the regular menu. I do remember my computer restarting with the Nano still connected when I was working on this problem early on. Could that have damaged something or reset something? I've spent hours and hours over the past couple weeks on this problem and I'm truly stumped. Can anyone help? At this point I don't know what else to do except take it back to Best Buy. Thank you in advance to anyone who can advise.