[TYPO3-calendar] Setting up caldav - DAV functionality does not work

[Ralf Thierfelder]

Dear group,
I tried to set up the DAV functionality with the extension caldav. 
(TYPO3 6.2.27, cal 1.10.3, caldav 1.0.1).
Following the manual I managed to get access to the calendar in the 
webinterface.
You can see a working example here:
http://www.green-bits.de/typo3conf/ext/caldav/caldav.php/calendars/kalender/Testkalender/
login: kalender
password: kalender

But I can not add the calendar neither to Outlook nor to Thunderbird 
lightening. I tried the following path: 
http://www.green-bits.de/typo3conf/ext/caldav/caldav.php/calendars/kalender/Testkalender/

What else do I have to configure to get a connection to the calendar in 
Thunderbird?

Regards
Ralf