More info:
It is something in the nrv2b utiltiy. The step that makes linuxbios_payload.nrv2b from linuxbios_payload.bin is what causes the problem. If I modify that to just copy in the linuxbios_payload.nrv2b built from the gcc2.96 toolchin, the resulting romimage works.
I looked at the latest nrv2b.c in util/nrv2b directory but there are only some printing changes...
-Dave