It is saying that the memory chips are not communicating with the bios. Modern memory have SPD ( serial presence detect )chips onboard that tell the bios what speed to run at.
It just means that the memory will probably just be running at the basic default setting of the motherboard. i.e. 66mhz, 75Mhz, 100mhz or 133Mhz. What ever is the lowest.
You should find a setting in the bios to alter the setting from SPD to the rams true speed. This would stop the message from appearing.