IPhone :: Duplicate Songs In 4S But Not In ITunes?

I have duplicate songs in my iPhone 4S. But everything is normal in library. I have unchecked the "Sync Music" and then tried to syncronize. I thought that this would delete all songs from my iPhone, so after that I would add my songs again and I would have solved the problem. Syncronization was completed but only the HALF of the songs were deleted. I couldn't delete the other half from my iPhone. I checked the "Sync Music" again and tried to sync again. Nothing has changed. I deleted my whole iTunes library and resynced again, nothing has changed.

In the end, I had to delete every single song one by one (I had like hundreds of songs.) with this "slide to reveal the delete button" move. Many people have asked about this problem in this support community but no stuff has brought a soluotion so far. This is sad, really sad.

Note: These music files can be seemed and played in iPhone but they doesn't exist in iTunes, you can only see the proof of their existence at the bottom of the device summary section in iTunes, I mean the size indicators.

Note 2: The proof I mentioned about is dissappearing temporarily when I check or uncheck the "Sync Music" checkbox. But after the syncronization it's coming back.

Note 3: The problem has occured this time (Yes, it happened few times before.) while I was texting to a friend during syncronization of new music files.

Info:
iPhone 4S, iOS 5.1.1, iTunes 10.6.1.7