boot0 is hanging...

[Pierre-Luc Drouin]

Hi,

I just did two different installations of 7.0-stable on a new machine 
and I have some issues with the boot0 boot loader. I have two identical 
drives on that machine. The first two slices on the drives are supposed 
to be bootable and they are mirrored with gmirror:

gmirror label -v -h -b load boot1 ad4s1a ad6s1a
gmirror label -v -h -b load boot2 ad6s2a ad4s2a

The problem I have is that I can only boot the second slice from ad6, 
not from ad4. boot0 does nothing when I press F2 from the menu for the 
first drive. I don't get any error message. It does nothing until I 
select another item in the menu. I can boot the first slice from either 
ad4 or ad6. I have tried rebuilding the raid and changing the priority 
of the drive with gmirror, but it didn't change anything. I also tried 
to remove ad6s2a from the mirror, but it didn't fix it either.

To install boot0, I used:
sysctl kern.geom.debugflags=16
boot0cfg -B -m 0x3 -s 1 ad4
boot0cfg -B -m 0x3 -s 1 ad6

What could be causing this exactly?

Thank you!