OK, got some setting ideas...
NOTE: my comments above and the setting below are based on an ASSUMPTION (dangerous, I know) that you have a "typical" system : Asus mobo, Q6600 CPU, 500W power supply (or better), DDR2-6400 RAM.
Gigabyte BIOS terminology may be slightly different than Asus but the functions will be the same.
Given: Q6600 CPU, DDR2-6400 RAM
Settings for best stability/timing ratios
CPU Clock Ratio: 8x
CPU Host Clock Control: Enabled
CPU Host Frequency (MHz): 400
PCI Express Frequency (MHz) AUTO (or 100MHz fixed)
Memory Multiplier: 2.00 (this sets the frequency to "800")
DRAM Timing: depends on your RAM specification, best set to AUTO for now
FSB OverVoltage: +0.1 V
CPU Voltage: 1.325 V
Save your changes and see if your boot problems improve or go away.
My CPU-Z screen shots.