I just got through two hours with customer service on this issue, and I am reording new RAM. I think the first problem is that when going through the compatibility tool drop-down menu, for some models it may recommended the wrong RAM. When I found my exact specs: iMac 2.8 GHz intel core2 duo (24 inch 800mhz), it directed me to an 800mhz RAM memory versus the 667mhz frequency. If you use one of your old 667mhz and one of the new 800mhz it will 'clock down' the new one to 667mhz and show 3GB of RAM -- fooling you into thinking that the RAM is OK and you bought the right product, BUT if you put both 800s in, then it won't work. You have to have one correct RAM in for the 'clocking' down to work apparently. So on one hand the tools that they have may be stearing people to the wrong frequency of RAM, BUT to give Crucial credit, they do have a warning to double check the frequency on the RAM before ordering -- which I did not. Apparently the best way is to do the system scan, but I hate downloading stuff. When I eventually did the system scan, it says I have the core 2 extreme and not the core 2 duo (which my mac says I have). There was my problem. I guess I will see if it works when I get the new RAM next week.
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