Hi Bill,
Just try to do "flash_eraseall" the kernel location (mtd3) and then check whether the u-boot boots correctly or not.
How did you flash the UBL and u-boot into NAND flash ?
Try to get the actual base address of UBL & u-boot and offset for both too.
Then mention in board file for mtd partition.
Do you have multiple copies of ubl or uboot ?
Please attach your complete bootup log.