Apple release iTunes 10.6.1 yesterday so you could upgrade and see if that fixes it or you could go the drastic route of uninstalling everything Apple and starting again.
1. Sign out of iCloud in Control Panel
2. Navigate to Programs and Features in Control Panel and uninstall all programs that are published by Apple.
3. Delete all Apple folders that were not removed at the time of uninstallation.
C:\Program Files\Common Files\Apple
C:\Program Files (x86)\Common Files\Apple
C:\Users\%USERNAME%\AppData\Local\Apple
C:\Users\%USERNAME%\AppData\Local\Apple Computer
C:\Users\%USERNAME%\AppData\LocalLow\Apple Computer
C:\Users\%USERNAME%\AppData\Roaming\Apple Computer
(REMEMBER to keep 'Bookmarks.plist') You will want to copy it back after re-installing Safari
4. Reboot
5. Install iTunes, then reboot
6. Install Safari,
copy Bookmarks.plist in to C:\Users\%USERNAME%\AppData\Roaming\Apple Computer\Safari, then reboot
7. Install iCloud don't sign in, then reboot
8. Sign in to iCloud then reboot
I cannot promise this will fix your problem but it is something to think about.