How long have you had the UV Lights in your system?
I had a problem where I recently installed a new 120mm fan in my system and it would work but then my system would freeze every now and then. Took off the 120mm and it went away. I bet you're just using up all of your PSU's juice. Unless it's a name-brand 350w or above, then it probably can't handle all the components.
Check the voltages (3.3V, 5V, +12V, -12V), that's usually a good sign of a dying (deathly) PSU.