Have the same problem with my new ASUS P5GD2 Basic; however, when I first set up the machine 1 week ago, I had connected the intrusion detector on the chassis (a Thermaltake Tsunami) to the mobo; during the trials I did not open the case.
and no problems were observed.
Last night, I removed the cables and opened the case to add a second SATA HD, and connect my chassis and CPU fans to a Aerocool Aerogate fan controller (I added power and ground cables to the sensor cable (yellow) heads - which enabled me to observe the RPMs on its own, but I could not control the speed - arranged the cables, also added a system speaker....
When I turned on the PC after this, I observed the "fatal error...system halted" message, removed the cover, removed the cable, shorted the jumper for chassis intrusion, however nothing happened...
Could this problem be caused by a fan cable shorting with the chassis? How could this happen after some minor modifications unrelated to the mobo in a functioning system?