Occasionally, and not immediately repeatable, W8.1 will freeze when a USB flash drive or wireless adapter, camera card or DVD is inserted. There is no keyboard input, mouse pointer is on-screen but dead. Reboot needed. No error message. Event Viewer lists "unexpected shutdown." There were incidents of this in W7 as well (same hardware). BIOS setting? Circa late 2011: I7 2600K, GTX 650, 8Mb RAM, latest BIOS Your thoughts welcomed.