Have been an anonymous reader for a while as I could usually find answers to my questions without starting my own threads. Not this time however... I have a mid-2009 MBP 15". It came with 4 Gb of Hynix DDR3-1066 memory that I'm now trying to upgrade in an effort to make the machine last me for another 1-2 years. Trouble is I can't make it accept any other memory except its original Hynix! So far I have tried 4 options: 1) Crucial RAM that was ordered from their website using their MacScanner tool. It was supposedly "guaranteed" to work but it didn't. Spent some time with the tech support on the phone and finally Crucial gave up on me and said to return the RAM to them. 2) Samsung 2 x 4Gb DDR3-1600. Computer doesn't boot and makes the "error beeps" immediately on start-up. 3) PNY 2 x 4Gb DDR3-1066. Same as Samsung above. 4) Corsair Value Select 2 x 4Gb DDR3-1066. Refuses to boot with both sticks installed. Boots up successfully with one of them or 1 Corsair + 1 original 2 Gb stick for a total of 6 Gb. However within 5 minutes OS goes into kernel panic. My personal conclusion from all the experiments is that my laptop is for some reason very finicky about the RAM it will work with. Anyone had a similar problem? Any advise would be appreciated? P.S. Additional details on the computer: it's a mid-2009 MBP 15" 2.8 GHz with AG-display running Lion with all the applicable updates including firmware. Optical drive was replaced by an SSD. It must have been one of the first in the series with the anti-glare display when it first became available (not hi-res).