I agree with Stimpy. I don't think the problem is with Outlook, it's likely to be something running on top of it, be it your anti-spam or your anti-virus. It may also be your anti-spam is anti your anti-virus...

From your symptoms, it sounds like something is checking every bit of information coming into Outlook (i.e., retrieving mail) or when Outlook is trying to access every bit of information (loading your mail for you to see), be it checking for virus or checking for spam (the anti-spam doesn't necessarily just scan mail coming in for the first time).

If you can track down what's causing the message as you outlined in #3, it may help. It's a security thing inside Outlook. It sounds like whatever is causing your grief is causing that too.

BTW, Outlook 2003 has a built-in spam filter. It's not excellent, but it's OK.