Can you perhaps give some more information about what OS/distro, which versions of Apache & PHP you're using; some log entry's perhaps ?
If you try to start it, and than give the command 'tail /var/log/messages' what is the output ?
Or perhaps cd into /var/log/httpd/ and check the output of those files (although there shouldn't be any entries, if i remember correctly).
BTW: Your e-mails don't work ?
what is the response of service exim status ?
If it's running you're able to receive mails, possibly the pop daemon has decided to kill itsself. But normally this wouldn't happen when there are Apache problems....