I installed my backed up copy of the XP OS on the newer AsRock Z77 motherboard. I then ran Converter Standalone which successfully converted the OS to a virtual machine that would run on the ASUS Z87 motherboard. New hardware to new hardware seemed to do the trick.
As I review the situation I suspect that the Standalone User's Guide warning that 'You cannot convert BIOS sources to UEFI destinations and the reverse' (found in the Supported Firmware Interfaces section) is what defines the problem. The ASUS P5 K is a BIOS board. The Z77 and Z87 Intel chipset boards are UEFI.
As an aside; all of the disks created by Converter 5.5 in my earlier testing (that would not boot) would in fact mount just fine. Examination of the mounted virtual disks revealed no problems, they just wouldn't boot.
I'm not sure the BIOS issue was the reason for my 'black screens' but moving the old OS to new hardware seems to be a reasonable course of action (It was all done in less than two hours. I had the Z77 back together before the kid got back from work).
rick shelby