Comment 28 for bug 41411

Oops, the Attach doesn't work too well... I'm pasting it here instead and hoping for the best.
Edit the file with sudo gedit /etc/fonts/local.conf and wait about 30 seconds before trying with OOo. As always, Your Mileage May Vary but I hope this benefits/helps others.

<!-- /etc/fonts/local.conf -->
<fontconfig>

<!-- Change the default Sans and Serif fonts in OpenOffice.org to the fonts from the ttf-freefont package. -->
 <match target="pattern">
  <test qual="any" name="family"> <string>Nimbus Sans L</string> </test>
  <edit name="family" mode="assign"> <string>FreeSans</string> </edit>
 </match>
 <match target="pattern">
  <test qual="any" name="family"> <string>Nimbus Roman No9 L</string> </test>
  <edit name="family" mode="assign"> <string>FreeSerif</string> </edit>
 </match>

</fontconfig>