Issue: Thesaurus function in OpenOffice.Org not working
Application: OpenOffice.Org Writer (v 3.1.1)
Operating System: Windows XP, Ubuntu
Enable the Language to use for that particular document / file.
Tools >> Language >> For All Text >> English (If this is the language you wish to use).
After doing this, you may now use the Thesaurus and Spell Checking tools of OpenOffice.Org