Recent security updates - now can't send emails

I have Windows XP with IE7. Automatically downloaded KB933729, KB939653 and
KB941202 yesterday. Now cannot send emails from OE using my email accounts
with outgoing mail authentication. Works for other email accounts. Incoming
mail works fine. Got my email provider to check their services - all OK. A
colleague has the same problem (different email provider). Tried Sys Restore
- wouldn't restore. Tried disabling all Norton virus, firewalls etc - no
change. Tried uninstalling the updates - no change. Anybody any ideas?

--
Richard