To update the translations to gnome-doc-utils:
* first update the docbook DTD in your translation
(for example de/netspeed_applet.xml) from 4.1.2 to 4.4

* then check if the old translated xml-file is valid:
"xmllint -valid de/netspeed_applet.xml 1>/dev/null"

* fix the errors if any (compare C/netspeed_applet.xml for reference)

* fix the structure of the .xml file, so that it has the same structure
as C/netspeed_applet.xml; you can verify this with 
"xml2po -r de/netspeed_applet.xml C/netspeed_applet.xml | less"
the translations should match...

* create the .po file:
"xml2po -r de/netspeed_applet.xml C/netspeed_applet.xml > de/de.po"

* fix the .po file: it's probably totally messed up; fix the translations
most of them should be there, but in the wrong place probably. translate
the rest

* for more info: http://live.gnome.org/GnomeDocUtilsTranslationMigration