iTunes cannot sync apps to the iPhone because the apps installed on the iPhone could not be determined
There are dozens of reports on this bug on the forums, and not one of the suggestions worked for me. After reading slocks post at https://discussions.apple.com/thread/3395256?answerId=17157627022#17157627022, I noticed that iTunes did indeed back up different apps each time I quit, restarted, and re-attempted sync, and that it always failed on the same one (USA Today in my case). I deleted USA Today from my phone, quit and restarted iTunes, and synced again. iTunes reinstalledUSA Today for some reason, but the sync completed then successfully, and all subsequent syncs also complete successfully. I then noticed that the App Store was promptimg me to update USA Today, which I did fully expecting that the update would cause the problem to recurr, but it did not. So it appears a corrupt app is causing this problem, and deleting the app from your phone may resolve it.
If you are getting this error, my suggestion is to watch during the sync, and note which application is being copied when the sync fails. Delete that app from your iPhone, and try to sync again. Please post the results here. Thanks!