"Enter Network Password" message in Outlook 2007

These seems to be an old problem, but I've not found a solution.

 

I'm running Outlook 2007 and using Go Daddy as my mail server. I have Norton Internet Security installed.

 

Every now and then Outlook "synchronizes" the files. When that happens I get a message to "Enter Network Password."

 

I've had this problem in the past, with my last computer, and it seems it involved a conflict between Outlook and the Norton product. But I can't remember how I fixed the problem, nor can I find a solution now.

 

Thank you.