Restarting did not solve the problem. I did a restore point from a from last week which seems to have solved the problem. Reinstalling the software updates which included one of the Visual C++ packs did not seem to break the Message Editor. Perhaps I had some malware keystroke monitor or something that slipped by the firewall and virus scanners. A full virus scan hasn't turned up anything.

I'm running v4.70 on Windows XP Pro

All of a sudden the formatting in the Message Editor has gone crazy.

 There is too much white space between words, but the paragraph format is set to left justify. Even the headers and quoted text is being spaced like this. I tried downgrading to v4.63 but the problem persists. I tried changing the fonts, tabs, resetting styles etc. but the problem persists. The text looks as if it is fully justified or tabs inserted instead of spaces.

The sent messages look as they should.

 Any ideas for a solution?

I recently upgraded some software that may have updated or the .NET framework on my system. Could that be part of the problem?

How does content look in other apps (Notepad, Wordpad, Word)? 

Have you restarted the PC?

A .NET upgrade should not affect Pegasus Mail.