Error doing partial update through update manager

[durga11]

I am using ubuntu 9.10.While running a partial update through System->adminstration->update-manager. I am facing error as 'Error Authenticating some packages".

Please find the attached, screenshot of the error and sources.list file output.

Thanks
Durga

[mörgæs]

Never do a partial upgrade:
http://ubuntuforums.org/showthread.php?t=1479146

They might leave the system in a state where a reinstall is the only way out.