I just had this very issue. I was installing a fresh OS on a separate drive and right as the computer did its final restart, the display just went black. No signal going to the monitor, two red lights on DRAM_LED and CPU_LED, it was just as you had described. I did what I've described below and it now seems that my motherboard can only pick up one drive via SATA at a time, which is why I tell you to make sure you only plug in the drive you plan on booting from. Not sure exactly what's caused this, or what I have left to do before everything is working as it once was, but I'm happy to be browsing the net and listening to music again, so hopefully this will at least get you to that point.
SOLUTION:Make sure you only plug in the drive you plan on booting fromClear RTC RAM as described in section 2.6 Jumpers of the manual here