This works:
a) close iTunes.
b) delete your iTunes Prefs:
MAc: ~/Library/Preferences.com.apple.iTunes.plist,
Win: Delete C:\Documents and Settings\username\Application Data\Apple Computer\iTunes
Delete C:\Documents and Settings\username\Local Settings\Application Data\Apple Computer\iTunes
c) Delete the "SC folder" (
Mac:
http://support.apple.com/kb/TS1389
Win:
http://support.apple.com/kb/TS1776
d) Restart iTunes
You will have to re-authorize. Otherwise you did something wrong ..
Regards,
Apple*