USB /root shutdown freeze

[markus at ing.umu.se]

I have 6.1-RELEASE installed on a disk in an external USB 2.0 disk 
chassis. It successfully boots a computer and becomes da0. However, it is 
not able to shutdown or reboot, as the system freezes before it shuts 
down.

--- begin ---
# shutdown -h now
[...]

System shutdown time has arrived
Shutting down daemon processes:.
Stopping cron.
Shutting down local daemons:.
Writing entropy file:.
Terminated
.
May 22 13:54:48 allegra syslogd: exiting on signal 15
Waiting (max 60 seconds) for system process 'vnlru' to stop...done
Waiting (max 60 seconds) for system process 'bufdaemon' to stop...done
Waiting (max 60 seconds) for system process 'syncer' to stop...done
Syncing disks, vnodes remaining...8 4 4 2 2 0 0 done
All buffers synced.
Uptime: 40s

--- end ---
This is the point where system stops doing things and not responding to 
anything but five-secs-powerbutton.

The system was installed by issuing

1. Regular FreeBSD install on internal ATA
2. fdisk, bsdlabel, mount USB-disk
3. dump | restore 
4. Fix fstab

The computer is a Dell Latitued D400 (the problem is reproducable on a 
number of other computers). The harddisk is a Maxtor DiamondMax 10 250GB 
IDE. The chassis is Amitech something.

I appreciate any ideas!


  - markus