Download AT&T Motorola Atrix 4G Android 2.3.4 Gingerbread Stock ROM

Here's a stock ROM 2.3.4 Gingerbread for AT&T Motorola Atrix 4G with lock boatloaders which can be flash.
This is a beta test firmware leak, an Android 2.3.4 for the Atrix includes full Google Talk with video support, although AT&T’s limited video chatting to WiFi connections.

Don't worry, they won't give you a brickable device like the over-the-air zip.
Briefmobile uploaded the stock images for those who want to check out 4.5.91 without trying a custom ROM or creating a brickable device.

You'll still need an unlocked bootloader to flash these images, but they should provide you with a clean version of 4.5.91 that works perfectly.

  1. Download moto-fastboot for your operating system
  2. Turn your device off
  3. Boot into "Fastboot mode" by holding down the bottom volume button while pressing power.
  4. Use the following commands to flash the images:
    • moto-fastboot flash boot boot.img
    • moto-fastboot flash system system.img
  5. Use the following commands to wipe data and reboot:
    • moto-fastboot -w
    • moto-fastboot reboot

Join XDA-developer discussion thread here for more details:

 Seems the stock ROM above causes a serious issues, jruweaver stated as of July 2011:

At this point it seems that once flashing this you may not be able to revert to a lower firmware without unlocking your BL! This build also may not receive OTAs. So in summary flashing this may cripple your ability to OTA!

URGENT!! Flashing any SBF 1.8.3, 1.5.7, or 1.2.6 using RSD after updating via this method results in permabrick!

Update January 01, 2012:
Good news! XDA-Dev Alaq had just cooked a new MFBSR script, this is another solution to revert the AT&T Motorola Atrix 4G  back to 2.3.4 stock.
Check out the full detailed guide and installation procedure prepared by Alaq himself. 
[Batch/Script] MFBSR - Moto-Fastboot: Stock Restore