Coolmax is a horrible PSU brand, it is definitely your PSU that needs to be replaced. If i was you, i would go with any of the following PSU brands, 650w or greater.
PC Power & Cooling Silencer series
Some OCZ PSU's are nice (do research on OCZ brands)
The following is a good example. The higher watt value you get, the more room you'll have for overclocking/SLI or Crossfire/future upgrades.http://www.newegg.com/Product/Product.aspx?Item=N82E16817139005