I Run rEFIt on a MacBook Pro (April 2010, 15", i7) with a Segate 500GB HD and OSX 10.6.5, Windows 7 and Gentoo Linux and everything was working fine! I replaced the HD with a Seagate Momentus 750GB 7200rpm HD (ST9750420AS) This is when the troubles began: Each time I install rEFIt, my MacBook freaks out with different symptoms: On Reboot ReFit does not start, it just boots directly to OSX, sometimes usbmuxd constantly respawns, WindowServer crashes, and/or mDNSresponder hangs. Mostly it just takes ages todo anything, sometimes the system doesn't boot but hangs at the spinning wheel. And every 2 or 3 boots, HD utility reports a corrupted disk ??? Similar to Bug ID 3147364, 3143295, 3016982, 3039932 It looks like rEFIt has some trouble with the 4k-instead-of-512b-Sector stuff of newer larger hard drives!