Strange email delay issue

Hello,

We have a user who is experiencing a bizaare issue. It seems to be random but has happened enough to raise concern. Some recipients are not receiving her email untill weeks later. There is no trace of it in sent items aswell. She does not use the delay option in outlook. This is a local issue as far as I know no external users have complained. On the exchange it is showing up as her sending it weeks later not when she claims. I have setup receipts for her after she sent the email so there wouldnt be any receipts but there also isnt any receipts when the exchange claims she sent the email. The issue is only happening to her.

we are running exchange server 2003 in a vmware virtual environment. users running on 2008 terminal services.

any ideas would be appreciated, thanks.