Anyone know what this error message means?

You should contact support they will give you help using the offline diagnostic tool it can be to do with system updates not too sure

Haven't seen this one yet. I wonder if it has any similarities to the E303 error.

Do you have a disc in the drive when you get this error? Or an external HDD?

If you do, try removing the said item, and then do a hard reset (hold the power sensor on the console for 10 secs, let it sit 10 secs, then turn back on) and see if it moves past that error screen.

Let me know if any of this helps.

I have this problem, what do I need to do?

support.xbox.com/.../system-updates-solution <-The error is covered in that troubleshooter. Did the steps work for you?

The error indicates there is an issue with updating the console. You will need to do an offline update

The step by step directions are on the site for the offline update (below)

support.xbox.com/.../system-updates-solution

To perform the steps you will need a USB device and a Windows PC as Apple is not able to use the format needed.

Initial update (right out of the box) - Click OSUDT1

Any update after - Click OSUDT2

If the updates fail you can try returning the console to the factory default and then again trying to apply the update to the console.

If this does not work you will need to visit
http://myservice.xbox.com , or contact support to setup a repair.

** Note: This is an offline update so you will need to be disconnected from the network, if unable to access settings unplugging the Ethernet cable or unplugging the router during the process will work