Itunes not moving past "preparing to update" while manually dragging and dropping music files

Hello there. I recently updated my iPhone to iOS 7.1. After the update, I noticed that I cannot transfer music to my phone by dragging and dropping. I though it may help if I upgrade my iTunes to the latest available version from the Apple website. That didn't help either. When I go to the "Apps" tab and drag and drop anything from the Windows Explorer to the apps, it gets added. It's only getting stuck at "Preparing to Update" when I add music from within iTunes library. If I disconnect during this sync and reconnect later, the songs do no appear in the phone but appear in the "on this iphone" tab as grey colored and cannot be played.
Any help wuld be appreciated.
Thanks. LD.

Replay

I have the same problem than you guys and I can fixed it just deleting the ebooks that I had on my device. I deleted them from iTunes on the device books list in my iphone. Presumibly some epub file was either corrupted or broken. I've got the idea and the possible reason from "twerppoet" at http://www.ipadforums.net/threads/help-my-itunes-are-taking-forever-to-update-fi les-on-ipad-when-i-transfer-ebooks.60436…
Hope that helps.