I can't find your MB in a quick search -- could you please post complete specifications for it (or a link to such specs)?
Here are some other possibilities for your instability problems:
1) Memory amount. First of all, you need 2-3GB for your system -- it's cheap now, so buy more to have a total of 2-4GB at least. Do this no matter what the problem is -- it will help your system performance a lot.
2) Memory instability. Download the bootable CD image of memtest86+ and run it for a number of hours to make sure you have no obvious memory errors.
3) Overheating of some component. Many water cooling systems have this issue, because although the CPU & other main component are cooled specifically, the general MB components don't get enough cooling airflow. For example, the north bridge and PWM (power circuitry near the CPU) areas can often overheat and cause system instability. The number of fans inside your case may not help here - it's also a matter of the configuration. Try running the system with the side of the case removed and a big table fan pointing into the case.