How come I have to reset my outlook.com password every few hours?

I am using Windows Live Mail 2009, with my outlook.com account. About 2-3 times each day, it says my account has been locked, and I need to change my password. How do I get this fixed? It's been occurring since my account was created. I posted this question on another Microsoft community site, but they say to clear my browsers' cache - I'm not using a browser.