Apart from the firewall (with you) this generally is a problem with the ISP, as for some reason you can't get connection.
I happen to have 2 computers. If one doesn't work I try the other and if that doesn't work either, I conclude that it's an ISP problem. A ping to the pop3-server gives the definite confirmation of that, but it might be that it does ping, but doesn't connect, depending on their error condition.
Contacting the helpdesk at such moments is very difficult (everybody phones at the same time), so I just wait and see till they solved the problem.
Often, if it's a problem with their pop3-server, their webmail works, so I can read and answer urgent mails that way. Then I send a copy of my own mail to myself (as bcc), so it comes into Outlook Express later on. Check if your ISP has webmail, and learn to use it.
If you don't have a second computer at hand, you might have a friend nearby where you can setup a dial-up connection to your ISP, and a e-mail account in some e-mail client. It should be password protected, of course.
Kees