Outlook 2003 hanging on "insert signature"

[hedera]

In Sept. 2008 I had a problem with Outlook 2003, on my Win XP Pro SP2 system,
going into a hang state while typing an email. Hang state was characterized
by a jittering cursor and the Outlook.exe process eating every available bit
of CPU. This issue was theoretically related to fix 931768, but in fact I
didn't correct it until I applied a registry hack that someone suggested:

Delete following keys, restart IE.
HKLM\software\microsoft\windows\currentversion\internet
settings\Zonemap\Ranges
HKLM\software\microsoft\windows\currentversion\internet
settings\Zonemap\Domains
HKCU\software\microsoft\windows\currentversion\internet
settings\Zonemap\Ranges
HKCU\software\microsoft\windows\currentversion\internet
settings\Zonemap\Domains

for all profiles. Also, we found it was part of the freaking default
profile for many machines, so we had to edit those as well.

This problem has just reappeared after 7 trouble-free months. I'll try the
registry cleanup, but: are any other Outlook 2003 users seeing this?

Is there any chance that applying Win XP SP3 would fix this? I held off
applying it because it didn't support ActivSync, which I use, but I see
ActivSync is now OK with it.