This may take a few posts to resolve.

Does it work correctly if run from a root login and fail when run from a regular login? If so, it's a permission issue. What do you get if you plug in your usb device and run the lsusb shell command as root and as a regular login?

I'm not a linux guru, but I did resolve permission issues with installing SANE drivers for a Kodak 5250 AIO printer/scanner with a USB interface. The fix involved creating and assigning myself to a group, in my case "scanner"(step 6) and creating a new rule in the /etc/udev/rules.d/ directory(step 7).

Have you searched http://help.ubuntu.com/community? Ex: search "setting usb permissions" http://askubuntu.com/questions/15570/configure-udev-to-change-permissions-on-usb-hid-device. Or search "udev syntax" http://askubuntu.com/questions/50357/how-to-run-a-shell-script-when-a-new-usb-storage-device-is-detected

Also google udev rules, ex:wiki.debian.org/udev or reactivated.net/writing_udev_rules.html.

As an example(from http://sourceforge.net/projects/cupsdriverkodak/forums/forum/2125778/topic/5396909)see the SANE Scanner fix below:

James

Thanks to all for your efforts in the development of the CUPS driver/S
+ANE backend for Kodak Aio printers!
 
I had previously successfully installed the CUPS driver and would now 
+like to document my experience installing the SANE backend for Kodak 
+Aio for an ESP 5250 printer.

 I run Ubuntu 10.10 on an old IBM Thinkpad laptop and I am a user rath
+er than a developer. This process took about 8 +/- hours of reading r
+elease notes, readme files, man pages, and forum posts and a good bit
+ of trial and error. Here's what finally worked for me: 

1. From sourceforge.net/projects/cupsdriverkodak/files/scanning-saneba
+ckend Downloaded kodakaio-02.4.tar.gz Extracted to /home/kodak direct
+ory 

2. Installed 3 of the recommended packages. libusb-dev was already ins
+talled on my system. sudo apt-get install libcups2-dev sudo apt-get i
+nstall libcupsimage2-dev sudo apt-get install libcupsdriver1-dev 

3. Followed Release Notes instructions: cd kodakaio-02.4 cd sane-backe
+nds-kodakaio-02.4 ./configure --prefix=/usr --sysconfdir=/etc --local
+statedir=/var BACKENDS=kodakaio make sudo make install 

4. Edited the file /etc/sane.d/kodakaio.conf # net autodiscovery (I do
+n't use wifi with this printer) usb 0x040a 0x4041 (ESP 5250 usb codes
+) scanimage -L still did not see the scanner 

5. Edited the file /etc/sane.d/dll.conf kodakaio scanimage -L now sees
+ the scanner as root only (Note: The Release Notes seem to be in erro
+r here, referencing kodakaio.conf instead of dll.conf. As corrected, 
+steps 4 and 5 should be reversed to match the Release Notes.) 

6. Created a scanner group using system->Administration->Users and Gro
+ups and added myself to this group. 

7. Created /etc/udev/rules.d/90-libsane.rules LABEL="libsane_usb_rules
+_begin" # Kodak ESP 5250 ATTRS{idVendor}=="040a", ATTRS{idProduct}=="
+4041", MODE="0664", GROUP="scanner", ENV{libsane_matched}="yes" LABEL
+="libsane_usb_rules_end" 

8. scanimage -L now sees the scanner as myself(and root)

scanimage > mytestscanfile Simple Scan XSane Image Scanning Program Ar
+e all working under Ubuntu 10.10 

I hope this summary helps someone save a few hours of research.
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