I am using Word 2003. Most Word documents are opening fine, but some quite slowly. I am trying to isolate the reason why this happens.

Of the ones which open slower, they appear to be those received as attachments in email. They are virus free, but for some reason they take maybe 20 seconds to open, as opposed to the normal speed. Its not every email received document, just some (very few actually but some!)

Can anyone suggest a way to check what is the reason.