Security Error in Windows Live Mail

As an experiment, to find out what part of WLM is causing it, I'd set the option to not "Automatically log on to Messenger" and to neither "Send and Receive at startup" nor to "Check for new messages..." Also, uncheck the option to "automatically download messages when viewing in the preview pane". Finally, open the Properties window and uncheck the option to "include this account..." for each mail account. Now when you open the program there will be no Internet access (except for the normal LiveID sign-in) so there shouldn't be a popup. The next thing to do is sync the mail for one account at a time until you find the one that causes the popup. It's probably one of the accounts that is not using "clear text athentication".