System crashes on USB connection

[Christoph Zep <debian-arm@quantentunnel.de>]

Hi everyone,

I installed Debian on a USB flash drive on my QNAP TS-419p+(Kirkwood) 
inserted into the lowest backside USB port.Everything's been working 
very smoothly until I tried to connect my printer to the NAS (also via 
USB). Via SSH the NAS reacted with the same error to every command as 
soon as the printer was connected:
-bash: /bin/dmesg: Input/output error

Upon manual power off (button on the NAS) and reboot, the system took a 
very long time to come up and finally booted. Since then, the system 
boots quickly againbut I don't know how to get my printer working.

Thanks for any suggestions,
Christoph