iTunes 9.1, which was released a few hours ago caused syncing issues for many users (specially on Windows), who were jailbroken on iPhone 3.1.2 (tethered) using blackra1n. But now thanks to ih8sn0w, this issue can now be fixed by using BlackBreeze.
To fix blackra1n RC3, simply start BlackBreeze and select blackra1n RC3. Now select the directory where you want to save the fixed blackra1n RC3 executable file. You’ll now notice that a new file by the name of blackra1n-fixed.exe would have been created in the directory where you chose to save it.
Now start this fixed version of blackra1n RC3 and use this to start your device (tethered). Once done, you’ll now be able to sync your iPhone (firmware 3.1.2) safely with iTunes 9.1.
UPDATE 2: Blackra1n for iTunes 9.1 has been released which like BlackBreeze, is another tool to fix Jailbroken iPhone 3.1.2 (tethered) devices sync with this latest version of iTunes!! More info can be found here.