ITunes won't recognize ipod after upgrade

Question

Yesterday my ipod synced fine, then I upgraded to the latest version of iTunes and now when I plug the ipod in, it does not show up anywhere. Nice.
I tried re-installing itunes re-booting and resetting the ipod countless times, different usb ports, etc. I'm convinced it is the software upgrade.
When I plug it in, it does not give the "do not disconnect" msg. It does nothing except indicate it is charging (little lightning bolt).
I had this same issue after an upgrade last year, and all the sudden it started working after simply plugging it in a few days later (magic!)
I also find it hilarious that one of the tips Apple suggests for this problem is to re-set your ipod to factory settings....which step 1 to do so is to connect it to your computer and select that in itunes--I can't get it to show up in itunes, so how can I re-format it!!
Any suggestions?
Are there any other files I should trash when deleting itunes off my mac besides the application?

Answer 1

OK, it is working now. Not exactly sure the cause of problem, but here's what I did in case others have a similar problem:
I did not have a syncservices file Carolyn mentioned.
So I hunted around and found a document suggesting to delete the ipod.plist file and the isync.plist file in the preferences directory.
I did it one at a time, rebooting both my imac and ipod before connecting again.
Deleting the ipod file did not work.
Deleting the isync file DID WORK. Also note that throughout this I had re-named my "iTunes" folder (where all my songs are), so when I opened iTunes, it created a new blank song library. Also, each time I did delete the itunes plist files mentioned previously in this thread.
Once iTunes recognized my iPod I went ahead and restored it, deleting all the iPod data.
I then restored my original song library to itunes, and re-synced the ipod.
Then the moment of truth, disconnecting the ipod and re-connecting to see if iTunes will recognize it. NO LUCK. SAME PROBLEM! %$#@&!
While I'm re-booting the mac, I was playing some videos on my ipod, I had not played in a long time. By pure chance I find that 2 of them appear to be corrupt and did not play correctly...they were very old qt movie of some commercials I had from 10 years ago, that I stuck on my ipod for fun last year.
I also found a video podcast I downloaded from Apple --the day I had these problems--would not even play. It played on iTunes, but locked up my iPod--my iPod has never frozen like that.
So I trashed those corrupt video files before I re-synced my ipod yet again (after restoring it again,etc.).
NOW IT WORKS LIKE A DREAM.
Not sure if a corrupt video file can hose up iPod syncing, but that is what the evidence points to here. Or possibly the older videos combined with the new software upgrade.
Thanks to Carolyn for suggestions.