German Language Support cant be installed in Dapper / Flight3

this is what i get if i want to install german language support for thunderbird-1.5 Maybe the locale-package is from 1.0.7? But why cant i
install the XPI: it also fails (see later on).

START OF INSTALLATION
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LC_ALL=C LANG=en_GB sudo apt-get install mozilla-thunderbird-locale-de
Reading package lists... Done
Building dependency tree... Done
mozilla-thunderbird-locale-de is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
1 not fully installed or removed.
Need to get 0B of archives.
After unpacking 0B of additional disk space will be used.
Setting up mozilla-thunderbird-locale-de (1.0.7-1ubuntu1) ...
Updating mozilla-thunderbird chrome registry...find: /usr/lib/mozilla-thunderbird/defaults/profile/extensions/: No such file or directory
mv: accessing `/var/lib/mozilla-thunderbird/extensions/installed-extensions.txt': Too many levels of symbolic linksdpkg: error processing mozilla-thunderbird-locale-de (--configure):
 subprocess post-installation script returned error exit status 1
Errors were encountered while processing:
 mozilla-thunderbird-locale-de
E: Sub-process /usr/bin/dpkg returned an error code (1)
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END OF INSTALLATION

Thunderbirds installer complains about:

..could not install this item because "install-u9w..rdf" (provided by the item) is not well-formed or does not exist.

I used the LANG and LC_ALL variables to have english error messages.

greetings, cozmo