Comment 3 for bug 150666

I have the same problem, here is the relevant aptitude output in english:
Setting up update-notifier (0.60) ...
/usr/share/gconf/schemas/update-notifier.schemas:12: parser error : Opening and ending tag mismatch: default line 7 and schema
    </schema>
             ^
/usr/share/gconf/schemas/update-notifier.schemas:14: parser error : expected '>'
  </schemalist>
          ^
/usr/share/gconf/schemas/update-notifier.schemas:15: parser error : Opening and ending tag mismatch: schemalist line 2 and gconfschemafile
</gconfschemafile>
                  ^
/usr/share/gconf/schemas/update-notifier.schemas:16: parser error : Premature end of data in tag gconfschemafile line 1

^
dpkg: error processing update-notifier (--configure):
 subprocess post-installation script returned error exit status 1

I took a look at /usr/share/gconf/schemas/update-notifier.schemas and line 7 looked like
       <default>false/default>

It should look like

       <default>false</default>

Making this small change fixes the problem.
Godspeed