dell poweredge 1950 : not rebooting under 6.1 (sometimes)

[Olivier Mueller]

Hello,

Another PE1950 question :)  Installation of 6.1 went well,
everything is working fine, even raid & scsi:

FreeBSD 6.1-RELEASE-p3 #0: Wed Jul 12 09:49:08 CEST 2006
    root at gi2:/usr/obj/usr/src/sys/SMP
CPU: Intel(R) Xeon(TM) CPU 3.00GHz (2995.51-MHz 686-class CPU)
ACPI APIC Table: <DELL   PE_SC3  >
FreeBSD/SMP: Multiprocessor System Detected: 8 CPUs      
[...]
mfid0: <MFI Logical Disk> on mfi0
mfid0: 69375MB (142082047 sectors) RAID


The only (very) disturbing thing is that it doesn't always reboot
correctely, when using "shutdown -r now" or simply ctrl-alt-del on
the console. 

It looks like that:

shutdown: reboot by om
...
Syncing disks ... 2 2 2 1 1 1 0 done
All buffers synced.
Uptime: 3m54s.

and then -nothing- : it hangs, but it really should reboot... 
Sometimes it continues with some lines about irq's, followed
by "Rebooting..." : all fine, but there is about 20% chances it
happens.

Any guess about what I should try?   I recompiled the kernel
with & without apci support or some different options, but it didn't
helped yet. 

regards,
Olivier