Okay - first, a caution. I have no idea what's going on ... so we'll have to try to work through various "fixes" to see if you/we can figure out what's going on...
1. On one of your many returns to 4.3.4, were you able to access the App Store then? Maybe you just need to "break through"...
2. Did you follow the steps in this sticky (
http://www.ipadforums.net/jailbreak...815-how-downgrade-your-ipad-ios-firmware.html) when you downgraded to iOS 4.3.3?
3. Did you jail break the iPad after the restore? Maybe doing so (via JailbreakMe.com, as it's the easiest) may help...?
Or, maybe try going with a fresh IPSW file of iOS 4.3.3, either from our link here or another trusted site.
That's all I can think of for now. Hope something there helps. Let us know?
Marilyn