I have a late 2009 i5 iMac and wanted to upgrade the RAM from 4 gb (2x2) to either 8 gb or 12 gb. I ordered some NuRAM (2x2) from OWC and thought everything was going fine. However, occasionally and EVERY time I restart or reboot the iMac, the computer becomes unresponsive with a black screen. The only way I could get my iMac to function is to take out the NuRAM and only use the stock Apple RAM. I thought there was a problem with the NuRAM and contacted OWC for a refund. I just received another batch of RAM OWC brand (4x4) and am having the exact same problems. Is anyone else having problems with 3rd party RAM? Any suggestions or fixes? Thanks for taking the time to read and your suggestions in advance.