Hello,
I had the same problem, outlook 2003 crashing. I've try to uninstall, reinstall everything [outlook (+ SP2), avast, msn toolbar,...]. I've try also to launch outlook in safe mode: outlook.exe /safe and it works.
In my case, outlook crash when i delete something : email, contact, appointment,... or when sending and receiving email. 2 month with the problem, 1 crash per minute... :'( so I was working with outlook in safe mode.
But I finally find the solution: tools, options, other tab, advanced options, and there is the "gestionnaire de compléments" (I don't know in english, it's the button above the COM button). I've deselected the avast4, and now everything is running fine !!!