OE sending emails to multiple contacts

My grandmother has a compaq running Windows ME (yes I know it stinks). It has Outlook Express version 6. She has comcast email and internet.

I have scanned it with Adaware, Spybot S&D, as well as Norton AV with updated definitions and the system is fairly clean.

From time to time when she tries to send an email to single contact, multiple people in her address book will recieve the same email.

There are a couple of things that might be a clue to the problem. About a year ago, I backed up her address book and emails and reformated then imported the account details using the process found here: http://support.microsoft.com/default.aspx?scid=kb;EN-US;q270670

The other thing I noticed, she has some contacts that are invalid. An example would be
Firstname.Lastname@whatever.net
Comcast mail server returns an error to outlook if this name is in the recipient list.

Any thoughts?

Thanks.

 

anyone?

 

help?