I assume that you are referring to Hotmail on the web. That would indicate that your account may have been compromised.
You may want to review this post:
https://windowslivehelp.com/solution.aspx?solutionid=6ea0c7b3-1473-4176-b03f-145b951dcb41
And also this blog entry from the Windows Live team:
http://windowslivewire.spaces.live.com/blog/cns!2F7EB29B42641D59!42740.entry
Help and Support for Windows Live Hotmail can be found at
http://windowslivehelp.com/product.aspx?productid=1
~ Microsoft MVP Windows Live ~ Windows Live OneCare| Live Mesh|MS Security Essentials Forums Moderator ~