For anyone who has seen this recently, here is how to stop it 
http://forums.mozillazine.org/viewtopic.php?t=584301
http://forums.mozillazine.org/viewtopic.php?t=584301
You may have been moved by Microsoft over to the new Hotmail Live 'service'
You can check this by logging on to the Hotmail Website... If you have been moved, you will get Hotmail Live, rather than the old classic Hotmail screen.
Go to Tools > Addons > Extensions and highlight the Hotmail Extension by clicking on the entry.
Click the Options Button.
Select Accounts > Mode for the account you are altering, and select the Hotmail Live (New Website) option.
Click OK to accept the changes.
Repeat for all affected accounts. (scroll bar at top )