I've got a user on an Exchange 2007 server (SBS 200

who is having a problem with never receiving certain e-mails. Which isn't exactly true. If I check the tracking and spam logs the e-mails are received and delivered to the mailbox, but the user can't see them in either Outlook or through OWA. But if I do an export of the mailbox the e-mails are definitely sitting in his Inbox in an unread state. I've reset his views but they still are not showing up. It is only happening to this one user. I don't see a pattern in where his e-mails go missing either, as it now even happens to my e-mails from an external account. Any ideas on this would be appreciated, I'm sure I'm missing something quite obvious.
Oh and yes I checked the rules there are none configured.