After upgrading to karmic 9.10 my Lightning extension in Thunderbird stopped working.
The method described on thread http://ubuntuforums.org/showthread.php?t=1145351 (a howto solving the same problem on 9.04) is not applicable on karmic 9.10 since libstdc++5 is not available through synaptic any more.
So I`m starting this howto explaining what worked for me.
First remove Lightning from Thunderbird: Tools->Addons, select Lightning, and uninstall and then close Thunderbird.
Don`t be afraid, since this will not erase your appointments.
Then install lightning-extension through synaptic or by just typing in a terminal:
Thats all you have to do. Now run thunderbird and watch it using lightningCode:sudo apt-get install lightning-extension
The extension in the repos is currently up to date.
Note 1: This is a universe package so you might have to enable them through system -> administration -> software sources.
Note 2: You might want (or not) install the package calendar-google-provider witch is suggested by lightning-extension