Hi and welcome to the forum.

Kernel 2.6.31-17 is available only on proposed repository, and I do not provide packages for proposed updates.
Anyway, you can easily build your own package starting from the packages sources.
There is no branch for 'nc10-backlight' on my launchpad account; instead, you can get the sources (.tar.gz) of the latest available version directly from the repository page (
link).
The version of the built packages is detected automatically during the build process by parsing the changelog, so all you have to do is to edit the file 'debian/changelog' and change the version to the one you want to build for.
In other words, change the line:
Code:
nc10-backlight (2.6.31-16~ppa1~nc10~karmic) karmic; urgency=low
in
Code:
nc10-backlight (2.6.31-17~ppa1~nc10~karmic) karmic; urgency=low
then use 'dpkg-buildpackage' to build the new .deb packages.
Obviously, make sure the needed dependencies for building the packages are installed (in this case, you need 'linux-headers-2.6.31-17-generic' installed).
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