try going to the FILE menu, then select CHECK PROJECT. then press the START button to have the program pinpoint the problems for you.

your buttons (and its highlights) might be overlapping one another. OR..

check if the MENU REMOTE is set to RETURN TO LAST MENU. to do this, click on a timeline. while selected, take a look at your PROPERTIES TAB, menu remote option should be there. select it. do the same thing to all of your timelines.

your main menu should be set as first play, unless you have a separate introductory splash video. end action for you main menu must be STOP.

does your menu have video thumbnails?