Reply typing is slow to appear on monitor

This is a new problem to me-just seemed to occur one day. When replying to a
message, if the reply is in HTML, most times-not 100%, but perhaps 90% of the
time the key strokes which should appear on the monitor are VERY SLOW to
appear-I mean like up to thirty (30) seconds after I stop typing. This can be
cured by changing the format to Plain Text (which I don't want to do!).
Does anyone know what setting can be changed to solve this problem-or why I
have this problem in the first place? How could everything be ok one day and
then have this problem the next without me changing anything? The problem
began with Office 2002XP and I couldn't solve it so I upgraded to Office
2003Pro and I still have the problem. I also added 1G of RAM.
Thanks in advance to anyone who can offer insight!
--
jhaz