I'm pretty much addicted to my iPhone but I believe I would've sold it for $50 the other day. It'd been several days since I updated my installed applications so I visited the app store to see what was new. I had 10 updates. Thinking nothing of it I began downloading all 10 application updates. After the updates were ready I connected my iPhone and started a sync. Halfway through the sync iTunes crashed.
I wasn't too worried about it and thought it was an isolated instance so I fired up iTunes and initiated another sync. To my dismay, iTunes crashed again, and again, and again. I wasn't sure what was going on so I started Googling and visiting the Apple forums to see if anyone else was having the issue. I began to blame the 2.2.1 version of the iPhone software I had installed only days before. I wasn't able to find much help on the Web but I kept troubleshooting on my own. I noticed that each time I synced one application would get updated and the next app update would fail. Looking at my iPhone, each app was getting updated and would run properly, but iTunes would continue to crash. I eventually got all my apps updated and was hoping the crashing would stop. It didn't. Even with no changes on my iPhone or Macbook Pro, iTunes crashed each and every time I synced.
It was as if my iTunes installation had a bad sync preference file or something. Late in the night I made the decision to completely wipe and restore my iPhone. It took about a half hour to get my basic iPhone setup going again without all my data and customizations. The problem still reared its head when syncing. I then went to the Applications tab of iTunes after selecting my iPhone in the left pane and told it NOT to sync apps. I then hit Apply and iTunes crashed while attempting to make the settings change.
So I plugged my iPhone in again and fortunately the "don't sync Apps" setting stuck. I hit sync, and it's now installing all my music, videos, and what not from my previous backup and subsequent restore. I then took the advice of someone in the forums and systematically uninstalled all non-default applications. That didn't resolve the problem.
Someone else in the forum indicated they had success with downloading all their apps again. I did a test with two different free applications and one paid application and each app install caused iTunes to crash.
After having enough I put away my computer in complete disgust. I was hating Apple!
If you are reading this and you're using Windows, the solution I outline below probably won't work. Several people who use Windows have contacted me to let me know they tried these steps and were not successful.
The next day I saw another forum post which recommended deauthorizing iTunes and then authorizing again. I disconnected my iPhone from my Macbook Pro, deauthorized then reauthorized, and then plugged my iPhone in and performed a sync. No crashing!!!!! So for a final test I downloaded several applications, some of the free ones I had and some paid (by the way you can redownload applications you bought without being charged) and everything worked.
I've now reinstalled everything and reconfigured all my data including how my icons are arranged. This was super super frustrating for me and I'm sure it was for the several dozen folks I've talked to with this same problem. Ack. Apple has lost at least 100 cool points and 200 product engineering points.
If anyone wants to follow the Apple forums thread that generated the answer to this problem, go here.