Meaningful Error Messages
I get this occasionally with the latest version of Microsoft's Outlook. Every now and again, I'll try to send an email only to be met with the message "The operation failed - an object could not be found". Fortunately, Microsoft supplied this highly detailed error message containing within it all the information required to rectify the problem.
The resolution for this error is to find any nearby object that comes to hand - a pencil perhaps, a policeman's helmet, a merkin stand, anything really - and offer this up to the screen whilst saying "Hey Microsoft, here's an object". Following this ritual, press the send button again and the email sends.
Works every time.