I bought this memory last month and about a few weeks later I started getting problems. http://www.newegg.com/Product/Product.aspx?Item=N82E16820231294 It started out that my mac would just crash (fubar graphics and then the "reebot your mac by holding the powerbutton msg")... Sometimes it wouldn't come right back unless I re-seated the DIMMS but as of the last week my mac would sometimes not come back from sleep and now I can only get my macbook pro to run if I remove one of the DIMMS leaving me with just 4GB. It doesnt matter which DIMM I use, both of them work on their own. But as soon as I combine the two it does not boot. I have no way to test the memory since I can't even bootup with the pair installed now. Kinda sucks since I just gave my old 2x2GB DIMMS to a coworker. I'm thinking I need to do an RMA with Gskill and that's going to be a pain in the ass I bet. FWIW I have a 13" MBP MacBookPro5,5 (Mid-2009).