OMG! I have been battling with this issue for 3 days now. I have had no trouble with syncing my iPhone 4S since I bought it a couple of months ago, although hadn't done one for a while, but this week none of my music would sync, it was all greyed out under my device, with my music library on my iPhone completely empty, and I have tried everything suggested on about 5 different threads and help web-sites, short of the restore option.
Thank-you, thank-you, thank-you Scnickr!
Your solution worked, or most of it did:
1. Close down all running programs on the Iphone (tap home button twice, then hold an icon until they wobble, then press close). (********Never knew this function existed....)
2. In Itunes, click your named device, then summary and check the box that says "manually manage music and videos".
3. Under your named device, click music, ctrl+A to select all. Right click one of the songs and deleted them all. Just make sure there's no greyed out songs showing. (*****I couldn't do this one - there was no way it would let me delete anything in the greyed out area under my device)
4. On the Iphone, select Music. I had this running so it was actually displayed on the screen which is what I haven't done before but don't know if it made any difference. (******This seems to have made all the difference.)
5. In Itunes, click your device and then click the music tab and select Sync Music and apply, then Sync in the bottom right hand corner.
And it worked. I am currently restoring all my gb's of music back onto my iPhone, and can look forward to everything getting back to normal tomorrow. Hurrah!
Thank-you again!