Intel ethernets disappear from x4100m2 BIOS boot device selection

I've got a weird situation that I'm hoping someone out there might have some
insight into.

The system is an x4100m2, originally jumpstarted with Solaris 10 over the
e1000g0 interface.  The interface has worked just fine for years, and has
always worked fine once the OS is booted.

Last year I went to netboot RHEL on the system and found that the Intel NICs
weren't trying to PXE boot -- after POST the system tried the NVIDIA NICs,
then went to disk without showing the Intel NIC initialization / PXE messages
at all.

I went into the BIOS setup and found that the Intel NICs no longer showed up
on the boot device order page.



Again, a booted OS saw and used them just fine, and ILOM saw them just fine:

-> show SYS/MB/NET1

/SYS/MB/NET1
   Targets:

   Properties:
	type = Network Interface
	fru_name = DUAL PORT GIGABIT ETHERNET CONTROLLER (COPPER)
	fru_manufacturer = INTEL
	fru_part_number = 82546GB
	fru_serial_number = 00:21:28:25:69:1E

Multiple rounds of setting optimal defaults in BIOS and powering off / on via
ILOM made no difference.

I opened a ticket with Oracle and after suggesting the above they replaced the
motherboard, and it worked again.  I netbooted RHEL over the interface and all
was good.

Now, some months later, the situation is back:  ILOM sees the NICs, RHEL sees
them, net2 works fine once the OS is booted -- but I can't for the life of me
get it to appear in the BIOS boot device menu.  I applied the latest ILOM
(build 58430) + BIOS image, with no effect.

Anyone have thoughts other than having someone on-site move the connection to
an NVIDIA interface and give up on the (superior) Intel ones?  At first the
NVIDIA interfaces didn't work for Jumpstart, though subsequent updates may
have addressed that -- I haven't tried in years.

Thanks for any insights into this situation.  Btrfs is a joke and I need some
ZFS love on this system.