I'm looking specifically for other 2.66 users with 4X2GB RAM installed. I want to know if you have been receiving any ECC Errors, which can be found under the Get Info/System Profiler/Memory. My errors have only come up in Slots 3 and 4, never 1 or 2. I have also swapped the RAM around and it didn't do a thing. You would also experience Kernel Panics in this case. I have had two Apple Certified Techs come to my house to first, install the logic board, that didn't solve my issues, so they came out again and installed a new memory riser card, that also did not solve the issue. So, now I dropped it off at my local Apple Store so they can run some tests to see if they can narrow down the issue. I have a third party DVD drive, PCI USB card, and OWC memory. I have also had OWC replace the memory one time with another new batch on the way. Has anyone else experienced this? If so, what solved your issue? I will also post what Apple has found when that time comes. It better get back to me sooner than later... I'm already missing it!