Can someone help me with my 27" iMac's Gray screen with 5 Pink Vertical Line Problem?

Question

Hi there,
I'm new to the forums, but I have a serious problem with my nearly 4 year old iMac 27" model.
I was using my iMac one evening and then suddenly everything displayed on the screen gets immediately pushed to the left of the computer screen. Then after a minute, my screen turns a solid gray, displaying no dock, no header bar, no options, and the keyboard and mouse suddenly disconnect.
When I turned back on my computer, it seemed to boot up perfectly normal. The normal gray start-up screen displays:
Then it displays the Apple logo and begins to spin the loading circle icon below it. But this time it adds 5 vertical pink lines down the screen from left to right. They stay in place the entire time:
And then when the login screen finishes loading, instead of bringing up my Account and my Password text box, it displays just a solid gray screen with the same 5 pink vertical lines on it, as shown below:
I've let it set for a half hour and nothing changes. During this time the keyboard and mouse seem to be disconnected, nothing seems to work with the screen or the computer itself. I hold the on/off button on the rear, turning it off and then on again. The same process happens with the boot up, the Apple logo appears, then the spinning loading icon below it, and then the vertical bars appear and the Apple logo and spinning icon disappear.
Is this a problem with the screen that an external monitor hooked up to it might fix, or is it a graphics card problem? I didn't buy the extended warranty package for the computer and it's roughly 3 1/2 years old.
Any idea what might cause this and how it could be fixed in the cheapest way possible?

Answer 1

I have the same problem since yesterday evening.
My google research found this:
iMac (27-inch): AMD Radeon 6970M Video Card Replacement Program - Apple Support
Maybe this is our problem. My iMac fits into this category.