looking for help about python-sane

[JW]

Sorry, I can't help much with the issue.  You are getting a low-level
hardware fault, and
not much information is being propagated up throught the system.  It's
not a Python problem, but something with SANE, and the Python wrapper
is just propagating the SANE error to you.  I have a few suggestions:

- Use a try block, and see if you can recover:

try:
     grabImage(webcam)
except _sane.Error, se:
     print se
     # but continue

See if all you get is errors, or if it's just a once-in-a-while thing.
Maybe you should sleep longer when you get an error, to give the system
a chance to do something else.

- Try to figure out if SANE is printing any logging message.  Check the
kernel log (dmesg), the normal system log, read SANE man pages, etc.
- Read the sane-v4l man page.  The one I found on the Internet says it
is Alpha software, which means it is highly experimental, but maybe it
has improved.
- Try a similar task using the native sane tools (sane-find-scanner,
scanimage, etc.).  This may generate more useful error messages.
- Post a question to the SANE mailing lists:
http://www.sane-project.org/mailing-lists.html

Once you have a happy SANE setup, then it should be trivial modify the
Python code to do the same thing.  Hope this is some help,
JW