I have a ubuntu server machine running 11.10 (not server edition) and sometimes when I do not do anything on the screen for a while, but I still use the services hosted on it from somewhere else on the local network, the machine suddenly goes into a coma. When I say a coma, I mean that the power light is on, the USB devices and CD drive have power and the fan is spinning, but the CPU light does not flash at all and it is not reachable over wired or wireless network, and the USB mouse and keyboard fail to wake it up. It is an "HP Compaq dc-7700 Small Form Factor" with an Intel Pentium D 3 GHz Dual Core CPU and Intel Incorporated Graphics chip.