8.0RC1: Can't mount usb-stick

I was able to mount and unmount my usb-stick today, but now it won't work  
anymore. I just plugged it in and can't mount it.

Output of dmesg:

ugen4.2: <JetFlash> at usbus4
umass0: <JetFlash Mass Storage Device, class 0/0, rev 2.00/1.42, addr 2>  
on usbus4
umass0:  SCSI over Bulk-Only; quirks = 0x0100
umass0:1:0:-1: Attached to scbus1
ugen4.2: <JetFlash> at usbus4 (disconnected)
umass0: at uhub4, port 1, addr 2 (disconnected)
(probe0:umass-sim0:0:0:0): TEST UNIT READY. CDB: 0 0 0 0 0 0
(probe0:umass-sim0:0:0:0): CAM Status: SCSI Status Error
(probe0:umass-sim0:0:0:0): SCSI Status: Check Condition
(probe0:umass-sim0:0:0:0): UNIT ATTENTION asc:28,0
(probe0:umass-sim0:0:0:0): Not ready to ready change, medium may have  
changed
(probe0:umass-sim0:0:0:0): Retrying Command (per Sense Data)
(da0:umass-sim0:0:0:0): got CAM status 0x39
(da0:umass-sim0:0:0:0): fatal error, failed to attach to device
(da0:umass-sim0:0:0:0): lost device
(da0:umass-sim0:0:0:0): removing device entry