I had the same problem. Try updating Ai Booster, BIOS, and nVidia NForce4 Chipset Driver (pay attention to its suggestions at instalation process) at www.asus.com.tw .
Then, forget about "AUTO" at "BIOS SETUP". Do your own choices. With a 11x Multiplier and a CPU Clock at 200 Mhz, and specially 2,80volts and 400Mhz for your memory modules (this has no overclocking for a AMD Athlon64 X2 4400+ which has a 2,2Ghz clock (look for yours); try 2,85 volts if you are running 4 modules). Ask your memory manufacturer the best voltage; these are at least voltage for CORSAIR modules (They told me that).
With this you should have FSB of 1000Mhz.
Regards, JJ.