Missing Accept Button On Meeting Requests (Outlook 2003)

I have a user who is saying that ever since Friday she has not been able to see an "Accept" button when she receives calendar invites, only the "Decline" and "Tentative" ones. She is currently able to accept them on her Blackberry, but does not want to have to do this every time she gets an invite.

On the Friday in question there was a monthly patch update that went out and she is fairly certain that this issue started after that - however there have been no other users who have reported this issue.

Does anyone know what may be causing it and how it can be solved?

Thanks