What CPU are you using , if you have a CPU that has a memory controller that runs at DDR3-1066 , then the DDR3-1333 might run but at the lower speed because of the CPU.
The CPU is an Intel i7 2700k
UPDATE: it's working now. I ripped everything out of the case and started over, triple-checking every element as I went along. Reseated the CPU, replugged all the essential components, etc. The RAM - and board - now work fine!