Same for me.

Thunderbird > Preferences > SOGo > Contact Caegories: pushing 'Add' or 'Edit' yield error message in separate window saying

XML Parsing Error: undefined entity
Location: chrome://sogo-connector/content/preferences/edit-category.xul
Line Number 21, Column 7:
<label value="&pref.categories.name.label;" control="categoryName"/>
------^

'Remove' seems to work though. The versions are

Linux Mint 13
Thunderbird 17.0.7
Inverse SOGo Connector 17.0.5

Most likely a localization error. Which language are you using?

Try to fix it yourself by modifying the dtd files.

Its the english version. Beside for spell checking (german) I cannot not find language settings. But the start page location value is

https://live.mozillamessaging.com/thunderbird/start?locale=en-US&amp;version=17.0.8&amp;os=Linux&amp;buildid=20130804001519

I cannot find dtd-files either.
$ find .mozilla-thunderbird -iname "dtd"
yields nothing.

There is another hint though. When I open Edit > Preferences the error console says

No chrome package registered for chrome://calendar/content/preferences/categories.js

with a bulb ahead. But thats all. Changing to the sogo tab, trying to use the Add bottom does not give more error message there.

I don't get any of these errors.

Try to search the dtd files in the SOGo Integrator/Connector extensions.

Thank you nonetheless for trying to reproduce that.

I went to the extension dir of thunderbird und unziped sogo-connector@inverse.ca.xpi . I guess I have to define
the entity "label" in one the dtds? In

chrome/locale/en-US/sogo-connector/preferences/preferences.dtd

it has

<!ENTITY sogo-connector.preferences.contacts.categories.none.label "None">

Does fixing mean to add such line in such file? By now I dont know which dtd-file to edit and what prefix to use. It actually seem a bit strange that the en-US localization has a gap.

Do you have Lightning installed?

That will fail if you don't.

That is embarassing, I havent had installed ligthening. Sorry. I did now and the error above does appear anymore.

Unfortunately, I still cannot try syncronization, because meanwhile my distro updated thunderbird to version 24.1.0. and the downloaded ESR-version 17.0.10 does not start. It says

./thunderbird: error while loading shared libraries: libstdc++.so.6: cannot open shared object file: No such file or directory

though /usr/lib/x86_64-linux-gnu/libstdc++.so.6 is in place. But I guess that is particular problem of my system.