Bad News! You can no longer update or restore your device to iOS 4.3.3 as Apple has closed down the signing window for 4.3.3 meaning that you can no longer restore a device to 4.3.3 in iTunes without previously saved SHSH blobs from that firmware. This news came from iPhone Dev Team member, Musclenerd, who tweeted this on his twitter account:
If you have already updated your device to iOS 5 beta without saving your SHSH blobs, then you are unable to downgrade your device. If you are already on iOS 4.3.3, then you don’t need to do anything with updating stuff. Keep iOS 4.3.3 to avoid any problem.