ITunes and IPhone no longer on speaking terms

Hello,

I'm hoping someone can help me with this. My iPhone apparently had a falling out with my iTunes and now I can't transfer music to the phone. iTunes will let me transfer new music files INTO it (like from a CD, or I can download a file off a blog and transfer those files into the "music" folder of iTunes) and I can create new playlists and transfer files into them from the music folder...but iTunes won't let me directly drag a file from the Music folder to the iPhone playlists and vice versa. The only way I can edit the playlists on my iPhone is to do it directly on the iPhone, or to sync the whole thing. The motherboard on my laptop started going bad a little while ago and I synced my whole music library to the iPhone to keep from losing those files, but I haven't been able to transfer those songs back onto the new laptop and I don't want to sync the whole library again 'cause I have nearly a thousand songs on the iPhone and I don't want to lose them...I just want to be able to edit my damn playlists and put a new song into the iPhone from my computer. My iPhone charges when I plug it into the computer, and I can transfer any purchases I've made FROM the iPhone into the music folder...I just can't transfer anything TO the iPhone and I can't use the computer to edit any of the playlists. I've tried reinstalling iTunes, but that didn't work. I hope it's something simple, but I don't really want to pay Apple for tech support if all I have to do is reset some preferences or something.

Help? Please?

Yours,
AE1981