The serial output shows that u-boot reported "Invalid board id! Can't determine system type for RAM init.. bailing!", which is what I got on my K4. It reports that message when deciding how to init DRAM, based on the pcbsn idme var. Right after the code reads that var (using idme_find_var?) I changed the return value to my original pcbsn. I also did that for the other known idme vars. Then it booted, and I used "idme -d" from SSH to write those to mmc.
But I was able to use MfgTool to run my custom u-boot.
EDIT: If you cannot build your own, it may be possible to patch my u-boot binary, replacing my idme vars with your own.
Last edited by geekmaster; 10-16-2012 at 12:13 PM.