Comment 3 for bug 368009

This is not a thujnderbird bug.
What error do you get when you try to add one? post the output if you run it is terminal (try both sunbird asnd thunderbird. I dont think you will get anything using lightning.)

What happens if you start a clean profile? are you than able to add it?
What calendar are you trying to add and how?
Does it help to disable the google provider extension?
What other packages related to lightning/sunbird do you have installed? dpkg -l lightning should show all including sunbird.

The main issues i have with this bug report is the extensions, the description and summary are not the same, it's lacking alot of basic information like what calendar you are trying to add does it happen with all google balendars?
I'm using 0.9 on hardy intrepid and Jaunty and i dont have any problems adding calendars,
I'm betting its google provider that is causing this issue for you. When you try a clean profile do not enable the extensions or you will still see same problem. Since you stated "I try with a new profile and only this 2 extensions : same bug"
From that i am 95% sure it is extension related.
The screenshot is unhelpful due to "cantadd....." where the calendar should be.
do you have the following installed?
calendar-google-provider

Before you do anything disable or remove google provider and restart the app and see if it fixes it. if not than with it still disabled use a new profile.