It is possible someone tried to hack into your account but efore you look into this though I would restart your computer This then completely restarts the program you are using to retrieve your mail. Sometimes a software like Mail for mac, outlook express and incredimail just need to be restarted. This often magically fixes a problem like this. If this doesn't work I would get a new email account and change the p***word ever so often from this point forward. I hope this helps.
There is nothing as fustrating as pop problems
