Try it with the factory installed OS.
i've had an acer m5811 for about 2 years now and just recently replaced the failing hard drive, we've done a very picky re-install of windows, scanned the new and old hard drive, checked the memory for errors and run just about every test we could possibly think of, but the computer seems to lock up while using any browser in general. explorer, firefox, chrome. it all locks up. we figured it might have been a network issue, but it seems to run online games nonstop for hours without issue, offline games work fine, and somewhere along the lines we blew a capacitor in the mouse, which still works, but shouldn't have the effect we're dealing with.
in short, computer mostly works fine, but shortly before and continuing after a clean windows 7 home premium install, the computer locks up while using internet browsers, but shows no other signs of network, heating or memory issues.