iPhone 3GS Stuck at Black Screen After Restoring and Jailbreaking iOS 4.3.3

Hello Joseph, you should not take your iPhone for warranty repair because Apple’s staff will refuse to fix your device because it is jailbroken. Anyway, you can easily fix this bug using the standalone TinyUmbrella (Fix Recovery). You can follow the tutorial posted below on hoe to kick iPhone out of endless recovery mode loop using TinyUmbrella (Fix Recovery):

Step 1: Download TinyUmbrella (Fix Recovery) for your Windows or Mac.

Step 2: Download Zlib1.dll from here and place it in the same location where fixrecovery43.exe is located.

Step 3: Connect your iPhone to the computer and power OFF your device.

Step 4: Launch iTunes as well as the downloaded TinyUmbrella (Fix Recovery) tool and put your iPhone into DFU mode.

• Press and hold the Power and Home button for 10 seconds.
• Then release Power button after 10 seconds but continue holding the Home button for another 10 seconds.

Step 5: That’s it! TinyUmbrella (Fix Recovery) will start fixing the error on your iPhone.

Anyway, have you upgraded your baseband to iPad’s 6.15.00 baseband? If no, then you should jailbreak it using either JailbreakMe 3.0 or Redsn0w 0.9.6rc19, instead of using PwnageTool or Sn0wbreeze jailbreak tools. You can check this blog post on how to jailbreak an iPhone using JailbreakMe 3.0. You can download Redsn0w 0.9.6rc19 using the following download links: Mac OS X / Windows. And the tutorial on how to use Redsn0w can be found here.