I've seen rounding errors with insufficient CPU voltage as well, so that's a possibility.
Don't increase the RAM voltage quite yet. You shouldn't have to do that unless you have four RAM sticks.
Do this first: Check your VTT/VCCIO voltage -- if it's not 1.15v, increase it to that.
If it still gives errors, increase the CPU voltage to at least 1.3v and try again.