What are the memory timings of the G.Skill Ram? Have you updated the BIOS to F5 or F6?
For example I have 2x2gb G.Skill RipJaws 1600MHz 7-7-7-24 2T, 1.6V.
In the BIOS, I set optimised defaults (which runs the memory at 1333MHz), and under 'Advanced Memory Settings' changed: DRAM Timing Selectable to [Quick] - This applies the ram timing settings to both Channel A and Channel B.
Then under 'Channel A Timings Settings', changed the first four timings to 7, 7, 7, 24 and Command Rate to 2T.
I left all the voltages on AUTO, which gives about 1.58V DRAM Voltage. Seeing as it's only running at 1333MHz, this is stable for me.
If I want to, I can overclock my CPU and run the memory at 1600MHz (using the XMP profile), but I don't have any want or need to overclock for now.