I have been running with this RAM in my MacBook Pro 17 (Summer 2009) for over 6 weeks. Not one lockup/freeze or problem of any kind. Programs are faster in general and I don't worry about closing applications any more. Apple computers through the years have been extremely finicky about RAM quality. I can't recommend these SO-DIMM's high enough. I put my old factory 2GB sticks for the MacBook Pro 17 into my wife's new MacBook 13. ..