My iMac is from early 2009 and currently is running Mavericks OS X and has 2 GB of RAM installed. I then purchased 2 x 4 GB strips of RAM that were manufactured by PNY. Specifically, DDR3 RAM which is compatible with 1333 MHz and 1066 MHz.
Once I inserted the RAM into my system after removing the previous RAM, it failed after working for only 5 minutes. However, shortly after, the system rebooted and continued to do this until I shut down the computer on the 4th boot. I then reseated the RAM and ran the system again only to receive the same results. Now that I have replaced the old RAM, the system is working fine.
Does anyone know why this might be happening? Note: this RAM is brand new.