FreeBSD unstable on Dell 1750 using SMP?

[Rutger Bevaart]

Argh. After all the fixes done on the 5.4-STABLE and 6.0 codebases my  
Dell PE1750 still reboots randomly. Again last night at 03.03 :- 
( essages still shows nothing, nothing special was going on at the  
time (loadavg ~ 0.00).

It's running:
FreeBSD xyz 6.0-RELEASE-p4 FreeBSD 6.0-RELEASE-p4 #0: Sun Feb 19  
21:15:01 CET 2006     root at xyz:/usr/obj/usr/src/sys/SMP  i386

What I've tried to fix the problems:
- kern_proc.c patch submitted to freebsd-stable by Don Lewis.
- disable HTT
- upgrade to 5-STABLE
- upgrade to 6.0-RELEASE-p1,2,3,4

What we've _not_ tried:
- Swap memory

This because we have 2850's that experience exactly the same  
problems, just less frequently (about once every 4 months).

I'm completely at a loss, and inclined to remove FreeBSD and install  
"another OS" as it is an important management machine for us, that  
reboots about monthly.

Any clues, tips, help, know bugs?

Regards
Rutger Bevaart