Same problem, this is how I resolved it.
Prior to the problem, everything worked.
RAM was Kingston recommended, etc.
OS install no problem, running good.
Fiddled with the isolated sata port and problem began.
The sata port that isn't in the cluster of four others and is next to the battery has an undocumented jumper, SPI_CON. The jumper falls off when you fiddle with that sata port.
Replace the jumper on pin 1-2 and you get a memory missing warning (3 beeps) on boot attempt.
Unplug the PC, let it sit for about 10 minutes, boot again and it boots normal.
There are additional complicating issues.
The board stencil labels the sata ports DIFFERENTLY than the documentation.
sata0 and sata1 are reversed in the diagram, but correct on the motherboard.
Be sure you are connecting sata0 to your boot drive.
If you followed the documentation and connected them backwards, it won't boot.
If you have 2 drives in your system, you might not realize which one is actually sata0.