problems receiving e mails - help!!

Hi I have suddenly become unable to send and receive e mails.

I keep getting a "Windows Security" box pop up asking for a user name and
password. I am unable to get rid of this box, however my password is correct
through my virgin media access to my blue yonder mail account.

I keep getting the following error message:-

Account: '', Server: '',
Protocol: POP3, Server Response: '-ERR Protocol error.', Port: 110,
Secure(SSL): No, Server Error: 0x800CCC90, Error Number: 0x800CCC91

Can you help?