Html vs Text slow process Outlook 2003

I mean since 1-2 week I discover that the new terrible slow time to
open a e-mail already received o a new message is due by html format
that I have always used before the slow problem
I checked that during the time that i wait (5-10 seconds) the process
of Outlook.exe will increase to 50% after the time and after the
message io opoened go down to normal activity.
Also if try to write into a new message there is a terrible slow time
before the caracters appear and it is impossible to write. If I change
the format into "norma" (no html) after second all become normal and I
am able to write normal. If I switch to html again slow time for
writing.
What could be? Any idea
I have Office 2003 SP2 with all recent update done (maybe one of
these ???)
Thank you
Faber