I had the same symptoms with a Biostar TA690 mobo. I guess we get what we pay for. I've replaced it with an Asus M2A-VM and the problems have never returned since then.
When you get a Biostar mobo that works properly, they run great and OC high given their cost. However, after buying about 5 Biostar mobos, I think they have like a 50/50 hit or miss ratio.
__________________ Main: Intel 2600K @ 4.8GHz | Gigabyte P67A-UD7-B3 | 16GB Corsair DDR3-2000 | 2 x 240GB Corsair Force 3 in RAID1 | 2 x 4TB Hitachi 7K4000 | 3 x 2TB WD Caviar Black | 3WARE 9650SE | Antec 1200 | Seasonic XP-860 Platinum | 2GB GTX 670 | 2 x 27" Asus VE278Q | Auzentech Prelude | Win7 Pro 64-bit |