My iphone keeps saying waiting for changes to be applied?

I'm trying to sync music from my computer to my iphone, it says waiting for changes to be applied for a long long time, i can sync my ipod no problem so what could be the problem!
when i plug it into itunes it doesn't give me the option to sync just goes 1,2,3,4, then 5 and won't come off of that!

There's a fix for that, but it isn't fun.

1. Create a backup in iTunes
2. Go to Settings > General > Reset > Erase all Content and Settings
3. Set up the phone and restore your iTunes backup (to put everything back on)
4. Sync. Viola!