Thanks Brian for trying to help. Here I am in northern BC on a slow link and unable to even re-install as I would do at home. I checked all the things you suggested; the problem persists.

This is driving me nuts. When composing a reply or a new message, the font changes to some fixed sized font, and EACH word entered is followed by a TAB. What did I do to enable this feature ?

[quote user="difficulty"]This is driving me nuts. When composing a reply or a new message, the font changes to some fixed sized font, and EACH word entered is followed by a TAB. What did I do to enable this feature ?
[/quote]

The font icon in found in the toolbar of a message window changes the font used in creating the message.  According to the manual this setting is sticky so check to see if the font being used could be the problem.

 Two other configuration areas to check:

- Tools|Options|Outgoing mail|Message formatting.  The information available through the help button contains the default settings for the tabs & margins so you can compare those to your settings.

- Tools|Options| User interface|Automatic formatting.  I do not have any of these ticked.