Help needed – strange problem with Outlook and exchange

Hello,
Has anyone got an idea on this problem.
We have a remote site in the us – running exchange 2003 – we are linked to out london office and have mails being sent back an forth.
A single user in the USA cannot open forwarded email with FW attachments on them from a user in our london office.
If the user sends this email it is 2meg in size and has about 20 attachments of emails.
I send to both the user in the US and to myself, I can open each attachment fine, but the user in the US see’s the attachments but when you double click on the attachment – it opens as a blank new email. According to the users inbox – there is data there – 2meg but when you try opening any of the attachments – they come out blank / new.
What do i need to look at as there are no limits set nor any spam filters enabled…. i just cant pinpoint this problem.
thanks