Posted about this before but got no response. Hoping someone else has had this problem and can help me get this resolved. I've taken it to the local Apple service center and they were unable to find any hardware problems, so I'm thinking it's a software problem. I'd rather not have to wipe the machine and start over, but it's getting to the point where I've lost enough work that the computer is no longer viable for work. The symptoms are as follows: * Machine locks up, cursor doesn't move, no keyboard input evokes a response * Always happens when Safari is being used and in focus (not in background) * After 20-30 seconds of being frozen, it powers down * Sometimes it stays powered off, other times it reboots. * Upon startup I get no error/crash messages, applications are re-opened * The machine acts like it's a cold boot.... not coming back from sleep. Unsaved work is lost. * Can't find any log messages, but I'm not super adept at knowing all of the places to look for those in OSX. * Happens when only Safari is running or when it's running concurrently with other apps (VMWare, RDP, etc). Worth noting, the logic board was replaced in December due to the VST problem. This didn't occur previously. When I left it with the service place, I wiped and did a fresh install. After getting it back, I restored from Time Machine. I can't readily reproduce the lockup. Happens on a variety of sites. Drudge, CNN, Macrumors, MSDN, etc. I usually notice it when it stops scrolling. Not sure if scrolling causes the problem or is simply the first symptom I recognize. Any thoughts on how I can triage this problem?