Is the problem necessarily that the file won't play, or the aspect ratio that you mention? Or, perhaps, both? If you are doing video out to a projector are you mirroring the displays? Where they are different aspect ratios and you are mirroring you can try to use them in extended desktop mode. Just open System Prefrences (Macintosh HD --> Applications --> Utilities --> System Preferences) then go to Displays. Choose the "Arrangement" option and then uncheck the "Mirror Displays" option. You will have to adjust how the screens are "arranged" and choose which you want to be the primary by clicking and dragging the apple system menu bar to the appropriate display. This might help if your problems are due to the difference in aspect ratio. Flip4Mac is a possible option, as suggested above, if VLC is being wonky at playing that particular video type.