Emails Disappearing from Outlook 2003 but not OWA

Hi,

I am having problems with disappearing emails. I am running Exchange 2003 and Outlook 2003. With some people an email will come in to there inbox in Outlook then disappear within 3 seconds to a unlnown location. I open up OWA and all the emails are there. I have made sure there is no filters, rules, .pst files, or Outlook settings moving the emails. I am at a loss. Can anyone help?

Thanks,
S