Are you attempting to run with both the DDR2 & DDR3 installed at that same time?
(That won't work.)
If you've removed the DDR2 & installed the DDR3 in its place, you would think it would work.
Is that particular memory "approved" for your board?
Will only 1 DIMM chip work in one or the other DDR3 slots?
Have you tried the jumper both ways?