syncing iphone

After I downloaded the new itunes, it wiped out my entire iphone music library. Fortunately the music on my MacBook is intact.

So I'm trying to sync my iphone with my MacBook but have had absolutely no luck. I have a MacBook Pro with 10.6.8 and an iphone 4. I tried doing a manual playlist sync (checking each playlist that I wanted synced) but it didn't work. I have restored and recovered the settings on my iphone and this didn't help either.

There's no music on my iPhone! Can anyone help?

I feel certain there is something you're not telling us. I have an iPhone 4, MBP and the latest iTunes (on 10.8.2) and it all works beautifully here.

Was this iPhone ever synced on another machine? Does it use the same iTunes account as the one you use on your MacBook?

I feel like I'm missing something, too, but I don't know what. It seems every time the itunes upgrades, there's a problem. But to answer your question, this iphone has only ever been synced with this MacBook Pro.

All my other software is up to date (I learned about that the hard way!).

What else could it be? I hate to take my stuff into the Apple store, they're such idiots.