IPOD sync incredibly slow

Hi - i hope someone has the answer to this - for some reason my ipod is taking an age to sync - about 5 mins per song! so it's been running for over 24 hours and still not done. I'm running vista ultimate with all the latest patches etc and version of itunes. When i plug the ipod in (same thing happens to my other 2 ipods) in vista scans them and always wants to fix them for corruption and adobe downloader always picks them up really quickly and scans at speeds you would expect of USB2. if i cancel out of the downloader and disk scan, itunes picks it up easily - knows how many tracks it needs to re sync and then starts syncing away.. but it takes an ages. Any offers of insight greatly appreciated. This is only a recent occurence.