Another iMac Freezing Issue - pls help a newbie out

Question

I understand this problem is not uncommon - I've been trying to read the many threads I see on the issue. However, most posts outline problems, suggestions are made, but then reported to not work. Also, many threads are 2 years old.
Could someone please suggest a step-by-step troubleshooting solution?
Here are my pertinent facts:
* Bought 20" iMac in July 07.
* Processor: 2.16 GHz Intel Core 2 Duo
* Memory: 3GB 667 MHz DDR2 SDRAM
* Hubs installed the second memory stick a while ago (over a year and i don't remember this problem correlating with the new memory).
* Video: ATI Radeon X1600
* OS: Mac OS X 10.6.2
* HD: 250GB capacity, 31GB available
* I am using an external harddrive to back up my stuff (LaCie, connected by firewire)
* Frequently used apps: Firefox, iPhoto, Photoshop Elements, Parallels (Quicken for PC), MS Office for Mac, etc.
The problem starting occurring several months ago, while I was still running Tiger. Have since upgraded to Snow Leopard, with no improvement, in fact, things are getting worse.
I get display distortion ("artifacts"?) - horizontal lines, blocks of the screen distort, usually clearing after dragging that part of the app off the screen of view and then back.
Typically, if I start seeing display issues, a freeze up is imminent.
Sometimes I get a sense it's coming soon - things run more slowly. Other times, it seems without provocation. I click on a window and nothing happens.
Sometimes it's the wheel of death other times screen completely locks up with no spinning wheel. No option to force quit. Mouse is unresponsive. Keyboard appears to be, although I can toggle the Caps lock button on and off (light toggles). If I am streaming video, the screen will lock up, but the audio continues. If I wait (have gone to bed and come back in the am) it is still frozen.
If I am streaming video (i.e Hulu on Firefox) or working in memory intensive applications (Windows, Parallels, Photoshop Elements, etc.) Problem is more frequent.
I can go a day or so without problems, but if I am doing anything slightly involved, it happens much more frequently, as often as every 10 minutes or half hour or so.
Steps I have taken:
I always have to do a hard reboot. I have run disk utility multiple times, occasionally it finds and corrects stuff, but no fix seems to be permanent.
I have seen suggestions of resetting PRAM as well as doing a clean re-install, but also seen that those fixes haven't endured.
I don't have Apple Care and I'm not sure what steps I should be taking to fix this. Is there hope? I mostly see lots of problems reported, but not successful resolution.
It's aggravating because I can't use the system for the stuff I bought it for (ex: digital scrapbooking) without worrying about losing my data. I switched to a Mac because I heard they ran so great and were "cool" to boot. While there have been many features of the Mac i enjoy, *if this kind of performance is typical after 2 yrs of use, I will not remain loyal to Apple.*
If you have been successful in resolving the issue with Apple, what did you tell them and what did they do?
I am competent system "user", but not as good when it gets into the weeds. Would appreciate any advice, feel free to spell it out as tho I were an idiot.
I would appreciate a "try this, then try this" approach, especially if you have tried it and it has worked for you.
Thanks for the help,
Kendra

Answer 1

OK, Mean, I mean Meanest, we have the same system (mine was purchased late 2006), and I can say we have identical symptoms. I agree with Paul_31 regarding disk space, but in addition, from all the posts on various Apple forums, it seems clear that the problem is due to the Radeon X1600 graphics card AND heat. These elegantly-designed Macs that we all love have a lot of stuff packed into a small package. Consequently they run hot, and over time the result is components bake and deteriorate. In our case, the weak link seems to be the Radeon card and since it’s not easily replaced, repair costs are nearly as much as the cost of a new iMac. A contributing factor is that over time dust will build up inside your Mac, and this serves as insulation, retarding heat transfer, and causing components to run hotter still.
OK, so that’s the sad tale, but what can you do? Assuming your system is not too far gone due to the ravages of heat over time, there are things you can do to help prolong it’s life, and hopefully get it to behave itself better until the time it finally fails completely.
In my case, the steps I’ve taken have resulted in a system that now “generally” runs for days at a time without locking up/crashing. A caveat: these are bandaids, not true fixes. I’m convinced the Radeon card will eventually fail and I’ll be faced with shopping for a new Mac – I’m only hoping the steps taken will give me a few more years of use before that happens. So, here’s my suggestions (basically they all have to do with getting your Mac to run cooler and being able to monitor temps so you know just how hot things are getting):
1. First of all, if you don’t already have one, get one of the free programs available to monitor your Mac’s internal temperatures. One of the most popular ones is a widget, iStat Pro. As I type this iStat Pro is showing my temps are as follows:
Hard Drive 92 deg. F
CPU 85 F
Ambient Air 69 F
GPU Diode (graphics card) 92 F
Hard Drive Bay 95 F
Memory Controller 90 F
Optical Drive 81 F
If you have iStat Pro and see that your temps are about the same as these, I would say don’t bother to read further – you may have a different set of problems. If your temps are 10-20 F (or more) higher, keep reading.
2. Try to clean out the internals of your Mac with compressed air. After 3+ years of use, I used an air compressor with an air gun attachment and blew through the vents at the back and bottom of my Mac with 60-80psi and actually saw a cloud of dust come out of my Mac. A more effective approach would entail cracking open the case of the Mac so you could really blow directly on the different boards/components. I haven’t done that, but I’m tempted to give it a try. Note: Some have suggested vacuuming and/or using a can of compressed air. I don’t think that approach is all that effective. You need a really strong flow of air to get that dust out of the inards.
3. Download the free program SMC Fan Control (v 2.2.2). It will allow you to adjust the fan speeds higher for each of the 3 internal fans. The Mac has firmware that ramps up the speeds of these fans as internal temps rise, but the general consensus is the Mac firmware is “too little, too late”. With the standard Mac firmware, the fans will run at their default settings well beyond the point where the components are already way too hot. SMC Fan Control allows you to set the minimum fan speeds higher than the Mac default.
Once you've done these steps, I'd suggest doing a SMC reset, then re-boot while keeping your fingers crossed.
This is getting too long so I’ll stop for now. Good luck...