I got an usb stick which contains some word documents, but from one day to another it stopped working (unknown usb device). I tried it on multiple machines and all giev the same error so its no driver or usb hub problem.
I haven't tried it in an linux environment yet, only in windows xp and windows 7. Not sure if linux is able to reconise it, if not is there anyway to make an image of on usb stick which isn't reconised as usb stick )
You may be able to create an image of the USB stick using a Knoppix LiveCD even if the partition does not mount. You will need to know what the device name is in the /dev directory. To find this out, try
sudo -i
fdisk -l
If the USB device is recognized then you can create a dd image of the device (/dev/usb1 or whatver it's called on your system) There is a thread with instructions on how to do this.
Data Forensics & Security Consultant