Spell Checker was not working in my install of OpenOffice.org3 on Slackware 12.1. Wrongly spelt words were not being highlighted. Pressing F7 after selecting text containing spelling-errors was not detecting any errors. After a lot of skulduggery and quite a bit of googling, I realized that the problem was some how related to locales, hence I added the following line to /opt/openoffice.org3/program/soffice -
Now spell checker works!