Receiving mail in Outlook 2003

I have Outlook set up to download all mail and leave a copy on the server. It downloads most of the mail, but leaves other mail up on the server. No rhyme or reason, and no error message. These emails used to download with no problem. No settings were changed before the problem started to occur.

Also, email filtering doesn't seem to work either. If I create a rule to send all emails with a particular subject to a folder, it works intermittently at best.

Any solutions?