What changed my email port settings?

Earlier this year, some update, I know not which, to Kaspersky AV 7.0.1.325 caused a problem opening the Thunderbird mail program.

Since then, I'd say that about 99% of the time I have to pause KAV to allow Thunderbird to open.
Tho annoying, this did not become a problem until 11 May 2009, at which time I stopped using dial-up and started using a cable modem to connect to the internet.

Needless to say, I was very uncomfortable pausing KAV as I was now continuously connected to the internet.

However, a few days ago, I found that the port numbers in at least Outlook Express and Outlook 2003 had been changed back to the default 25. I forget whether Thinderbird was affected.

This happened only on my Win 2000 system which is hardwired to the router.
Vista system, wireless connection to router, was not affected.

I am in the process of doing a full KAV scan of the Windows 2000 system.
No issues were reported on the OS drive.
And I do not see any issues with the Run and RunOnce keys in the registry.

I know now that I needed to disconnect the cable modem briefly while KAV is paused.

What are the possibilities?

1. A virus that snuck in while KAV was paused, did its damage, then destryoyed all evidence of itself?
2. An abberation caused by IE 6 or Windows, or the mail programs themselves, changing the port number?
3. Is this the type of problem that should have been caught by the router's firewall? I guess that I need to ask D-Link if I have the right settings for the router and firewall.
My incoming and outgoing mail servers are at different ISPs.

Any ideas?

 

The move from dial-up to btoadband was on 11 May, but the problem did not occur until 22-23 May.

However, there used to be a Comcast DEsktop Doctor icon, and it seems to be gone now.

Also, the Comcast Toolbar and Comcast High-Speed Internet Wizard are listed in Add/REmove programs.

I should likely get rid of all the Comcast stuff.
I'll give Comcast a call.