I tried Googling this, but came up with some old posts about the old iPods, but nothing on the iPhone. Basically I can sync my iPhone to iTunes, but anytime I try transferring any music or videos or even podcasts to it, it doesn't work. The only way I can get them on there is by making it so it automatically syncs music, but after that when I try to select music on my iPhone it's greyed out and I can't do anything. I'm using a jailbroken 1.1.2 by the way.

when using an iPod, you can easily drag and drop musics from your pc to your ipod, but with the iPhone this is not possible...

All you can do is sync all musics, or, if you dont want all of them, create a folder and sync that folder only... Also, in iTunes, you cant play musics from your iPhone directly, you have to play them from the computer... If you want to make a test, connect your iPod and dont select manually manage songs, select to automatically sync, you will see, it will happen tha same that happens to you with the iPhone

To sum up, if I got what you said, you dont have any problem...