are you installed to HD? easiest way to insure Openoffice is English is to remove the German-English version (apt-get remove openoffice* ) & replace it with the standard version but you can only do this if installed to HD. Don't know if there is a .deb for Openoffice, go to the OpenOffice site, download their package & use the installer that comes with it.
Bonus: you then get full set of help files which I don't think are include with Knoppix for space reasons.