Can't receive email

All of a sudden, I can't receive email in my Outlook Express account. I can
send email*, read newsgroups, but can't receive it.
*I can send it if I click on "Send Now" in the email toolbar. If I compose an
email and click on "Send and Receive All" in the OE toolbar, the composed email
goes to the outbox. There are three emails in the outbox, but when I open the
outbox, I can't see them. There's an error attached to one of them, I thought
if I could delete it my problem would be solved, but as I stated, when I click
on outbox, it opens but does not show any email in it. I have made no changes
in any settings, TCP/IP, OE preferences, etc..