[Fyre4ce]

A brief history: bought the machine around the beginning of 2007, ran 10.4 until a couple months ago when I started to have some issues with strange behavior and freezing, including horizontal lines appearing across the screen. Problems became so severe that the computer became unusable - would freeze doing almost anything. I upgraded to 10.5 in lieu of reinstalling the system software and that solved the freezing, but the horizontal lines remained, and some other "artifacts" occasionally appear on the screen. Hard to describe, but sometimes when scrolling a square or triangle won't scroll while the rest of the window will. Sometimes the shapes are shaded colors rather than an old image. I have screen shots that I can post if I can find a way to host them.

Anyone ever encounter this? Would there be any benefit doing a reinstall? Could this be a hardware issue?

Thanks!

[kmkkid]

Sorry but your graphics card is fried.

It's a somewhat known issue, most likely caused by heat.
The same happened to mine a few months out of warranty, luckily after a year later apple replaced my logic board for free.

I'm surprised they haven't issued a recall as many have had the same issue.

Edit: mine was a CD iMac
You can try calling up apple and bitching, ymmv.

[Fyre4ce]

I called Apple and it sounds like they're not going to fix it for free. That would be a long shot - computer is almost 3 years old. So, my options are to either take it to a retail store and get it repaired for $300-$500, or buy a logic board on eBay and do it myself. Two questions about this I would love to get answers on:

-How hard is it to get the case apart and replace the logic board? I am used to rebuilding things, but don't know if there's a risk of cracking the plastic case, etc.

-Can I put in a logic board from another iMac, either due to availability of alternate hardware, or for performance enhancement? I saw some 2.8 GHz logic boards for sale. Anyone have experience with this?

Thanks

[kulverse]

I had the exact same issue only worse. On a warm day, you couldn't see much of anything and the computer would freeze. Did some research and found out that the GPU is overheating.

I have run flawlessly for over 6 months now after installing the following application and turning up the fan speeds. it's little louder now, but it went from useless computer to perfectly working computer

Fan Control

It's says it's for MacBook, but works flawlessly on my 20"iMac

[Fyre4ce]

Originally Posted by kulverse 

I had the exact same issue only worse. On a warm day, you couldn't see much of anything and the computer would freeze. Did some research and found out that the GPU is overheating.

I have run flawlessly for over 6 months now after installing the following application and turning up the fan speeds. it's little louder now, but it went from useless computer to perfectly working computer

Fan Control

It's says it's for MacBook, but works flawlessly on my 20"iMac

OK, so I guess I will hold off on getting a logic board from eBay. I wonder why the problem started like it did - maybe dust accumulation? Also, I don't usually hear the fan running; I wonder what that means.

I think I will first try to reproduce the problem by running it in my bathroom with the heat turned way up, then maybe clean it inside and out for dust if that makes it worse. If that doesn't fix it, at least I will have some practice disassembling it for a logic board swap later.

[kulverse]

Originally Posted by Fyre4ce 

OK, so I guess I will hold off on getting a logic board from eBay. I wonder why the problem started like it did - maybe dust accumulation? Also, I don't usually hear the fan running; I wonder what that means.

I think I will first try to reproduce the problem by running it in my bathroom with the heat turned way up, then maybe clean it inside and out for dust if that makes it worse. If that doesn't fix it, at least I will have some practice disassembling it for a logic board swap later.

It's a known issue on our machines that Apple refuses to acknowledge. It's nothing specific that happened while you had it. It just started happening on my machine after a year or so. The Fan control utility works though