You probably assigned a macro to the keystroke combination. Review your macros and assign a different keystroke combination to the macro. Even if you don't have any macros saved in the current document, there might be macros available because they are stored in Normal.dot or because you have another document opened that has macros.
If you are in a dialog box and have made a mistake while the recorder is on, click the Cancel button of the dialog box or press Esc to close the dialog box. None of your selections in the dialog box will be recorded. If you have already completed the command or closed the dialog box, then choose Edit, Undo, and the last command will be removed from the macro. If too many commands have been chosen, use Edit, Undo, and edit the macro when you are finished recording it. Remember which command you want removed. The macro statement you want to remove will have a similar name.