itunes doesnt sync music

Hello.

i have strange problem. When I connect my phone with itunes I have two problems:

1. iTunes displays all my iPhone Content as "other files". Only if i change the e.g. sync mode the real types like music, apps, photos will be displayed for a short time. after applying the change, iTunes says I only have "other files" in my iPhone

2. I cannot sync my iphone. The sync button is always greyed out. I can select and deselect music and apply it. But afterwards even if new music is selected, I cannot sync.

Thx for your help.

sven