For those still using the old Outlook Express, we recently had a computer that had a weird symptom. When "Send and Receive" was clicked to check for new email, outlook express would present error 0x80004005.
In researching the error a bit, Microsoft has a knowledge base article that didn't really apply, mentioning a corrupt ".mbx" file... probably inbox.mbx. This didn't make a lot of sense, since I couldn't find an .mbx file on the computer, and Outlook Express uses ".dbx" files to store email.
After a little more research I came across an interesting comment on Yahoo! Answers that mentioned this error code and checking Yahoo mail via the POP protocol. Hey! This machine is trying to check Yahoo mail (well an sbcglobal.net address anyway)!