I am one of the many people who has experienced this problem after upgrading to iTunes 4.5. I have a 20 GB iPod which I bought at the Apple store in the Mall of America in January. There is a fix to this solution and it has worked for me. Go to Apple's web site, choose the Support tab, then choose the Discussions sub-tab, select the iPod product forum, then select the [regular] iPod, and then the Usage folder. The posting is currently second from the top and is called "iPod doesn't appear in Updater or iTunes in Mac OS X". The instructions were fairly straightforward, at least for Panther users.