ipod touch stuck on itunes sync

Hello,

since about a week itunes and my new ipod touch (4G) are stuck on sync:

• itunes starts syncing when ipod is plugged onto the computer
• itunes shows it's spinning circle and the message "wait for sync to start" and "step 1 of 5"
• the ipod shows the spinning arrow-circle, too
• nothing happens - the sync process hangs
• after a long time, itunes falls back to normal state (display switched to empty) - without having synced
• on the ipod, the spinning arrow stays spinning, even if it's unplugged again from computer

Yes, I tried every measures to get them to work together again, but nothing works:

• plug off an in ipod before and after start of itunes
• restart and hard restart ipod by pressing standby button and standby plus home button for 10+ seconds
• dismissing itunes preferences from the library folder

Strange enough:

• the file transfer from and to the ipod apps via itunes continues to work.
• itunes tells me (in the overview pane), that the last ipod backup dates from three hours ago - when sync failed: Can I believe this message?

Now I don't know what to do next:

• Reset the ipod via itunes or preferences app?
• What will happen to the files and apps on the ipod?
• Can I restored them from backup?
• Will my music collection be restored (from iCloud)

Any help is welcome - thanks in advance.