using scanner causes contents of usb buss 001 to disappear, scanner does not work

I am trying to use scanner on my pixma mp500 . I needed this and found that my wireless connection went offline. Looking at this some more, I see that the printer also disappears from the bus and I have to shutdown to get back to normal, a restart does not work. I installed xsane which does the same as the simple scanner although it does show that it is looking at the mp500.
Surely nothing should be able to "crash the bus"?