USB drive not detected at boot

[Brad du Plessis <bradd%cat.co.za@localhost>]

Hi all,

I've got a number of unmanned systems that use external USB hard-drives 
for backups (on netbsd-4). The problem I've seen at a few of them is 
that the drives are not detected at boot and dmesg shows the following 
suspicious message:

uhub7: device problem, disabling port 6

A reboot sometimes resolves the problem and dmesg then looks like this:

umass0 at uhub7 port 6 configuration 1 interface 0
umass0: Sunplus Technology Inc. USB to Serial-ATA bridge, rev 
2.00/c6.83, addr 2
umass0: using SCSI over Bulk-Only
scsibus0 at umass0: 2 targets, 1 lun per target
sd0 at scsibus0 target 0 lun 0: <ST310005, 25SV, > disk fixed