I just found this on two other forums…
Latest IE Update & SpywareBlaster = Outlook 2002 Problems?
http://www.dslreports.com/forum/remark,18312763
IE7 and Outlook HTML e-mail create is slow
http://forums.spybot.info/showthread.php?t=11047
Outlook is scanning the entire listing of Restricted Sites (ZoneMap) entries in the registry on every single keystroke in HTML editing mode. This obviously causes an extreme slow-down of Outlook - to the point where editing messages in HTML mode can be nearly unusable.
Plain Text mode or suggestions noted in these links will solve this issue.