MS OE6 cant read e-mails by outlook2000

I have 2 WIN98SE pc’s both have outlook 2000 and outlook express6 installed.
One pc however can not view the contents of an e-mail sent by Outlook 2000.
The e-mail arrives as and looks normal but when opened the contents are no longer there.
I an attachment has been included then the paper clip does not show either in the inbox.
It is only happening to one pc out of the 100 I am looking after. Any Ideas as this is getting annoying.