Dear all,

I ran into these problems when I tried to connect my digital camera to my computer after using a USB memory stick. The stick was on /dev/sda4 and the camera on /dev/sda1. When I tried to mount the camera I got a pop-up saying "/dev/sda1 is not a valid block device".
I do not know how to realy solve the problem in a nice way, but a manner of living with the problem is to remove the usb-storage module and then initialize it again. To do this, use
<unmount and plug out the device you used.>
modprobe -r usb-storage
modprobe usb-storage
<plug in and mount the device you want to use.>
in a terminal. Most likely you have to login as root to do so.
I'd love to hear better solutions.

cyclotron