We got problems making X8SIL work with KINGSTON KVR1333D3D4R9S/4G memory chips:
http://www.ec.kingston.com/ecom/configurator_new/partsinfo.asp?root=&LinkBack=&ktcpartno=KVR1333D3D4R9S/4G
If I am not mistaken, KVR1333D3D4R9S/4G meets mobo requirements but after installing these modules in memory slots, "non supported" led blinks. Can you please cast the light on the potential culprit?
It is correct type, but you will need to use X3400 CPU as CPU determines which memory types can be used.
If you use L3406 or Core i3 or other CPU, then you can only use UDIMM.