I am running iTunes 220.127.116.11 on Windows 8.1. I have an iPhone 5 on iOS 7.0.4.
First of all I NEVER experienced any major problems with itunes on windows running an iphone 4 for the past several years, nor with my iPhone 5 before the iOS7 update.
The first problem I started experiencing was that iTunes was forcing me to sync apps that I had already deleted on my phone...apps that I had never even installed on my iPhone 5 but only on my old iPhone 4. This got so bad I pretty much stopped syncing my phone because it was so annoying. However then I started experiencing an issue where my phone would no longer sync new music.
To be clear, if i downloaded a new song it will NOT sync to my phone from itunes. If i update a playlist, the playlist update will NOT sync to my phone. Nothing related to music will sync anymore. Not only that the phone UI started going through crazy loops in the music app when I would play certain songs. I assumed somehow my phone had become corrupted.
I thought maybe my iPhone had a damaged OS or something so I just did a restore on it back to 7.0.4. This worked. I also deleted and re-installed iTunes. However when I went to sync my first playlist on the newly restored phone, iTunes throws errors that music files cannot be read and the sync stops. These files play fine in iTunes. The error does not discrimiate between my legacy MP3 files and my newly purchased itunes files, i just encounters a file it does not like and stops my sync.
At this point I have a reset iphone missing all my apps which STILL will not sync my music. Honestly the state of this software on windows right now is SHAMEFUL. If anyone can advise I would really appreciate.