slim try the following settings man:

NB GTL = +40mV
CPU GTL = -21mV
CPU GTL = -24mV
CPU GTL = -24mV
CPU GTL = -21mV
CPU VTT = 1.4V
NB Voltage = 1.66V
SB Voltage = 1.65V
Place a fan over the northbridge cooler to keep it cool, and try various FSBs.
The following settings should be ok for FSBs up to 475MHz ( QDR1900 )