I am running Windows 7 64 bit with a Dell 755 PC. If the PC is disconnected from broadband, and it is idle for several minutes, when I wake it up from sleep mode, the PC can shut down unexpectedly (then it is rebooted automatically). If the PC is connected to broadband, it does not have any problem. I have updated to the latest version of BIOS, but it does not solve the problem. The problem repeats itself each time I disconnect from broadband and let it idle for a while. What can I do ?