Video add-in returns "unexpected error"

[Rusty]

I have Outlook 2003, Windows XP (up to date), latest DIrectX, latest Windows Media - and when I try to send a video message I get an error message that it had "encountered an unexpected error." This must surely rank with the great error messages of all time. Unfortunately, I am not one of the great error message interpreters of all time
What does this mean, and what can I do about it