This error is usually caused by an object or file that is currently open in another program with an active modal dialog pending. ...

This error is usually caused by  an object or file that is currently open in another program with an active modal dialog pending.  A modal dialog requires an answer and suspends use of the object or program  until the dialog is resolved. To resolve this problem, select the program with the open object from the task bar and then close any open dialog boxes with pending requests to the object.