Received emails appearing blank when sender uses plain text - Outlook 2007 SP2 - Windows 7 Pro - Dell E4200

We have a client who is receiving blank emails when there should be text.
We've found out that this only happens when the sender has used plain text. HTML emails are received without issues.
No one else appears to be experiencing this issue on the same network using the same outlook version.
He doesn't have any anti-virus scanning emails.
Updating his outlook fully did not make a difference.
Looking in some forums suggested altering the Stationery theme within outlook from none to blank, but he hasn't got the blank option there to try this.

Anyone else experienced any issues like this?
Anyone have any suggestions on what I could try next?

Thanks.