I just received and installed a 4gb kit from Crucial in my iMac 2.4GHz Intel Core 2 Duo. When both pieces were installed the machine would not boot. I took them out and swapped sides and the machine booted up and appears to be working fine. However, when I go to "About the Mac" it tells me I only have 3GB of 667 MHz DDR2 SDRAM. What about the other gig????
Does the computer recognize the full amount of memory if you reinstall your old modules? If it does, please try the new ones one at a time, to check how much they read as when installed alone. Each time, please ensure the modules are fully seated, and leave the other memory slot empty.
Please also give us the full CT part numbers you have as well as the outcome of the above, and we can proceed from there.