Hi all, A couple of months ago, I had issues with a 5400 RPM SATA 2, Seagate Momentus HD with my Unibody MacBook. It worked fine in Windows (and in a USB caddy), but I kept having random beachball lock-ups in OS X and "waiting for boot device" boot failures (crossed circle on the screen) , as people are seeing when running SATA 2 drives in the new MacBook Pro. I put an identical Momentus HDD in my girlfriend's white NVidia MacBook at the same time as I got mine. It was working fine. She wanted to put 3.0 on her iPhone recently, so upgraded to 10.5.7. As soon as she did this, she got the same symptoms I had been seeing. I then thought - did 10.5.7 change the MCP79 drivers? I had a look with Pacifist and saw that it did update AppleAHCIPort.kext (amongst others). So, I moved the old one (in System/Library/Extensions) and replaced it with one from a downloaded 10.5.6 patch. Then, I removed /System/Library/Extensions.mkext (This is regenerated by the system, and ensures no cached kext's interfere with my tinkering). I've been using the system for a few hours and the beachballs seem to have gone. Also, I have restarted it about 40 times, and not seen any boot failures. Does anyone technical want to try this on their uMBP to see if it sorts their HDD issues? It might screw your system up so watch out. I'm loathe to call it a fix as yet, as I would like to use my system for a few days first.