Sounds more and more like you have an unstable BIOS ... from what I saw on that board at ASUS (see link I provided above) ... there's only one BIOS listed. It may be an update, or the original that comes with the motherboard. Confirm the version that is currently running on your mobo, then back it up using ASUS's BIOS utility. Then try installing the (newer) BIOS version. If the version already on your motherboard is in fact the same listed on ASUS's site ... then I would still backup your current BIOS and reinstall with the downloaded file.
If you have trouble figuring out how to back up your BIOS ... the utility should ask you if you want to back up your current BIOS before installing the newer version at some point during the installation.