Default dictionary changing

[USAOz]

When I first installed Outlook 2003 from my Office 2003 CD I selected the
AUSTRALIAN DICTIONARY as the default spelling dictionary.

I had to do a Detect and Repair to my Office 2003 installation due to a
problem in Excel 2003 - I assume that such repair checks ALL Office 2003
components - including Outlook 2003.

When I check under Tools/Options/Spelling/International Dictionaries, the
Australian Dictionary is the one shown (others are in the drop-down menu).
To ensure that is the one I am using I selected and applied that option.

NOW when I create a NEW message, the correct dictionary is used.

BUT if I REPLY or FORWARD any message that contains words spelled
differently in Australia than in the U.S., the U.S. Dictionary is used
instead of my default selected Australian Dictionary and NOTHING I do will
change that!

When spellcheck occurs, a word is selected as misspelled so i select the
Australian Dictionary and proceed until next misspelled word pops up and its
back to U.S. Dictionary again!

What is happening and how do I force ONLY the Australian dictionary to be
used for both new messages and replies/forwards?