though it's most likely GPU related literally means the console does not know what is wrong. possibly a short or cold solder joint somewhere. So far there is 1 major theory for what causes most of these errors is that the Ram, CPU, or GPU are not soldered properly to the mother board due either to poor manufacturing or excessive heat up and cool down cycles that stress, weaken and eventually break the soldered connection.
There are two theories to fixing this one deals with the "X" clamps that hold down the chips. The other involves re-Heating the chips. DO NOT attempt either of these if your console is still under warranty. If your console is still under warranty return it to the store where it was purchased or call MS to have it replaced. I have also heard of limited success by simply switching the AV cable from "HDTV" mode to "TV" mode.