Here are a couple of things to check:
1) Start by setting your defaults to English (Canada) in Office Language
Settings application -- Start->Programs->Microsoft Office->Microsoft Office
Tools->Microsoft Office Language Settings->Enabled Languages tab. It's the
dropdown at the bottom of the dialog (assuming you're in Office 2003 or
Office 2007)
2) After restarting Word, turn off "Detect Language automatically" in your
language settings dialog within Word (Tools menu in 2003, Review tab in
2007).
3) And to fix the current doc you will have to select the text and apply
English (Canada) again from Word's language settings dialog.