Hi there,
I've tried a couple of USB 2.0 DoC (memory sticks) today. While they 
work fine when one reads data, they fail on write.

Here is what I get:

umass0 at uhub2 port 1 configuration 1 interface 0
umass0: Pen Drive USB DISK 2.0, rev 2.00/1.00, addr 2
umass0: using SCSI over Bulk-Only
scsibus0 at umass0: 2 targets, 1 lun per target
sd0 at scsibus0 target 0 lun 0: <, USB DISK 2.0, PMAP> disk removable
sd0: 246 MB, 984 cyl, 32 head, 16 sec, 512 bytes/sect x 503808 sectors
[...]
umass0: Invalid CSW: tag 55518 should be 55519
umass0: Invalid CSW: tag 55519 should be 55520
umass0: Invalid CSW: tag 55520 should be 55521
umass0: Invalid CSW: tag 55521 should be 55522
umass0: Invalid CSW: tag 55522 should be 55524
umass0: Invalid CSW: tag 55523 should be 55525
umass0: Invalid CSW: tag 55524 should be 55526
umass0: Invalid CSW: tag 55525 should be 55527
umass0: Invalid CSW: tag 55526 should be 55528
umass0: Invalid CSW: tag 55527 should be 55529
umass0: Invalid CSW: tag 55528 should be 55530
umass0: Invalid CSW: tag 55529 should be 55531
umass0: Invalid CSW: tag 55530 should be 55532
umass0: Invalid CSW: tag 55531 should be 55533
umass0: Invalid CSW: tag 55532 should be 55534
umass0: Invalid CSW: tag 55533 should be 55535
umass0: Invalid CSW: tag 55534 should be 55536
umass0: Invalid CSW: tag 55535 should be 55537
umass0: Invalid CSW: tag 55536 should be 55538
umass0: Invalid CSW: tag 55537 should be 55539
umass0: Invalid CSW: tag 55538 should be 55540
umass0: Invalid CSW: tag 55539 should be 55541
umass0: Invalid CSW: tag 55540 should be 55542
umass0: Invalid CSW: tag 55542 should be 55543
umass0: BBB reset failed, TIMEOUT
umass0: BBB bulk-in clear stall failed, TIMEOUT
umass0: at uhub2 port 1 (addr 2) disconnected
sd0(umass0:0:0:0): generic HBA error

And also : wtfs: write error for sector 2624: Input/output error

This is a memory key of dubious origin.
With another key from SanDisk, a "cp" hangs forever, no error message is 
displayed, and the disk can be unmounted. After reboot, the file is 
there, but there is no way to recover the prompt after the "cp" command.

Has anybody a clue?
Cheers!
Vincent