Ruth- A couple of years ago I had this problem intermittently with the version of Outlook Express I was using, but not with full Outlook 98. That was with Win95A. Recently I moved to Win95B with a new hard drive(Yes I know that everybody else had long since gone to Win98) and find that everything is rock solid.
But the recent thread about setting the language encoding to English makes me wonder if that could possibly make a difference in loading UFT after using Outlook. So I would suggest clicking on Outlook View-Encoding and setting the code page to one of the Western European options instead of Auto Select.
It may be that just surfing the net causes the selected option to change. It may be a relevant variable that must be reset to prevent a crash.