How to fix “iTunes could not back up the iPhone” error

After updating to iTunes 8.1.1, i started seeing this error when my iPhone was connected to my Mac Pro on Mac OS X 10.5.6.

I could get iPhone to synchronize with iTunes but i could not backup my iPhone. I thought a reboot would help but instead it got worse. After a reboot, i could not even get my iPhone recognized.

This is what i did to fix this problem:

1. Delete iTunes from Applications folder
   
2. Kill iTunes Helper process using Activity Monitor
   
3. Delete /System/Library/Extensions/AppleMobileDevice.kext
   
4. Delete /Library/Receipts/AppleMobileDeviceSupport.pkg
   
5. Delete folder /System/Library/PrivateFrameworks/MobileDevice.framework
   
6. Empty trash
   
7. Reboot Mac (this step is important)
   
8. Re-install iTunes