Ever since i upgrade my 2G iPhone (on T-Mobile USA) to beta 3 from beta 2, i have not been able to back up my iPhone. I keep getting this error:

iTunes could not back up the iPhone "ktula's iPhone"
because a session could not be started with the iPhone.

Anyone else having the same problem ? This is on Mac OS X 10.5.6 running iTunes 8.1.1.

After rebooting my Mac Pro, it got worse. I could not even get iTunes to see my iPhone.

This is what i did to fix it:
- Deleted iTunes from Applications folder
- Kill iTunes Helper (using Activity Monitor)
- Deleted /System/Library/Extensions/AppleMobileDevice.kext
- Deleted /Library/Receipts/AppleMobileDeviceSupport.pkg
- Deleted folder /System/Library/PrivateFrameworks/MobileDevice.framework
- Rebooted Mac Pro. This step appears to be essential. I did the previous five steps without rebooting and i could not get iTunes to see my iPhone.
- Reinstalled iTunes

Originally Posted by ktula

After rebooting my Mac Pro, it got worse. I could not even get iTunes to see my iPhone.

This is what i did to fix it:
- Deleted iTunes from Applications folder
- Kill iTunes Helper (using Activity Monitor)
- Deleted /System/Library/Extensions/AppleMobileDevice.kext
- Deleted /Library/Receipts/AppleMobileDeviceSupport.pkg
- Deleted folder /System/Library/PrivateFrameworks/MobileDevice.framework
- Rebooted Mac Pro. This step appears to be essential. I did the previous five steps without rebooting and i could not get iTunes to see my iPhone.
- Reinstalled iTunes

try re-installing SDK, i had same issue before and re-installing SDK fixed the issue and iphone shows up again under devices in itunes.