You try to use your scanner with XSane but it says that it cannot open the device and gives you the error «invalid argument»? If so, I may have an easy solution for you!
First of all, and after ensuring that you have the package sane-utils installed, open a terminal and run «scanimage -L». Look at the command’s output for the line matching your scanner, which may be something like «gt68xx:libusb:001:005 is a Mustek BearPaw 12: f00 CU flatbed scanner». If your line starts the same way, that is, with «gt68xx», then keep on reading! (If not, then I’m sorry but you’ll have to look somewhere else for instructions on how to get your scanner to work).
Alright, so now that you know for sure that your scanner works with the gt68xx driver, you only need to do one thing: install the firmware for your model. This is a «.usb» file which you can find in the driver CD for your scanner or at this website: firmware for gt68xx scanners, and you only need to copy it into the directory «/usr/share/sane/gt68xx/».
I have tried this with a Packard Bell Diamond 1200 Plus, which needs the firmware file «PS1Dfw.usb». So, I just copied that file from the driver CD (it’s in the directory WinXP; note that, if you prefer, you can also download the file from the above mentioned webpage) to my home folder and then using the terminal moved it by doing «sudo mv PS1Dfw.usb /usr/share/sane/gt68xx/» and set the right permissions for it with «sudo chmod 644 /usr/share/sane/gt68xx/PS1Dfw.usb».
That’s it, now you can go to Applications -> Graphics -> XSane Image Scanner and it will work just fine :).