i haven't seen this, but i have only been booting my USIIIi systems
lately. i'll try the SB2000 soon and see what happens. but first,
let's gather some more info from your crash:
trap type 0x68: cpu 1, pc=410657c0 npc=410657ac
pstate=0xffffffff99820092<,PEF,IE>
Skipping crash dump on recursive panic
panic: +fast data access MMU miss
cpu1: Begin traceback...
cpu1: End traceback...
cpu0: shutting down
cpu1: rebooting
can you use gdb or addr2line to convert pc=410657c0 and
npc=410657ac into file/line numbers? (you probably will
need to build your kernel with -g for this to work, add
this to your kernel config: makeoptions DEBUG="-g")
can you set sysctl -w ddb.onpanic=1 and when you get the
db> prompt, see if 'bt' works there as well?
.mrg.