Hotmail are rejecting IceInSpace generated emails at the moment, due to a mail-server problem we had last week.
So if you have a hotmail email address listed in your profile, you will not receive any PM email notifications, subscription notifications, activation emails (for new registrations) or password change emails.
In the meantime, you can change your email address to a non-hotmail one, or sit tight and hopefully the issue can be resolved with hotmail in the next few days.