Comment 1 for bug 120564

Hi Neville,
It could be possible that the thesaurus wasn't installed with open office. Here's how you can check to be sure:
Click system --->Administration--->Synaptic Package Manager
Then type in your administrative password

Next press the search button on the second toolbar. Type in "openoffice.org-thesaurus" in the first box and select "name" from the second. Press search.

A list of thesauruses should come up. Look for the one for your language. If the box on the left is shaded in than the thesaurus is installed. If not; right click the thesaurus on the list, and then click "Mark for installation" Then press the apply button. This will install the thesaurus.
When the installer is done, you can close it. Open up openoffice.org and see if the thesaurus works. Good luck! Post back here if it works, so we know that the bug was solved.