Enter Network Password Problem

I am using Windows XP Home SP3. I have Outllook 2007 and Verizon is my internet provider. Just recently and periodically a dialog box pops up and asks for my network password. (See screen shot attachment). I do not know why this is happening. I have been using Outlook for years and the 2007 version since last summer. I started by just clicking Cancel and went away and then a few days later it came back. Then I typed in my password and clicked OK and then it was fine. It came back again today. I do not have a Network in my home.
Is there an explanation for this and a way to stop this dialog box from re-appearing?
In Outlook I do have my username and password saved.
Thanks

What happens when you place a check mark in the box REMEMBER My Password?

When I put the check mark in it still came back. It actually came up a few minutes ago.