SharePoint offers the "Spell Check" feature in its "Rich Text Fields"
In our custom SharePoint application,we have utilised the "SharePoint Spell Check Web service".
There has been a few bugs that has been identified with the SharePoint Spell Check,The Microsoft's QFE Team was involved in fixing the same and delivering back the "private hot fixes".
It was observed that the "dictionary language" defaults to "English US" although the "locale = English Australia".
This issue is being currently investigated by the Microsoft Support Engineers and also by myself.
There is a likelihood that,this could be because of the "language" selection during the install of SharePoint or may be it's a bug..
Will keep you guys posted soon.