I've had this problem before, and now a friend of mine is having it. When a new message or query is sent, a window will not open up for the message or query.

Is there a setting that needs to be changed or does the program need to be reinstalled?

Are you ignoring the user? Do you have any scripts running? Any of these could be the cause. More information is needed, specifically the results of typing /ignore -l and //echo -a $script(0)