System hanging, error messages with USB drive on FreeBSD 8.1

[Brett Glass]

I'm working with a FreeBSD 8.1-RELEASE/amd64 machine that's 
attempting to write data to an ordinary Kingston 8 GB microSD card. 
The card has been inserted into its USB adapter and plugged into a 
USB port on the machine. The system is locking up repeatedly with 
messages that say

(da1:umass-sim1:1:0:0): SYNCHRONIZE CACHE(10). CDB: 35 0 0 0 0 0 0 0 0 0
(da1:umass-sim1:1:0:0): SCSI sense: Error code 0x52

A Web search reveals that problems like this have cropped up for 
many, many FreeBSD users as far back as 4.x. But I can't seem to 
find any solution (which amazes me; if there's a bug, one would 
think it would have gotten some attention). Do I have to abandon 
the use of FreeBSD with USB thumb drives (or maybe with USB 
altogether)? Hope not, but I may have to if I can't get this fixed.

--Brett Glass