Today someone started to complain that whenever he was trying to access the hotmail website he got a invalid certificate message and when he was trying to login with MSN messenger he received a 80048412 error. After a quick search the solution was quite easy. Somehow he managed to reset his date to somewhere in the future. So error code 80048412 in MSN messenger, look if the date is set correctly. If not, set it to the correct date and try again.
Just one of those things you can search for hours for if you do not know it.