If it's timing out when receiving from a POP3 account, there may be an email stuck. If you have webmail access to that POP3 account, try going in that way and deleting the oldest email, then try again. You might also try calling the ISP to see if they can kick that one email out for you.
Of course, there are other things that affect POP3 email accounts such as the reliability of the communication line between you and the POP3 server or the time of day (is it peak rush hour?). And, it could be on their end as well. Maybe their server is occationally "busy". If the mail eventually comes in, chances are this is the problem.
Occational problems are difficult to track down. Sometimes it's a simple matter of having to wait it out.