This is weird

I have 1080p 24fps footage.  I set my sequence up to be 1920 x 900 p  24fps.  When I drop the footage in the time line it looks great.  If I export it like that it looks great, but if I render the timeline then all of a sudden there is a few pixel black bar that sits at the bottom of the program monitor and it will export that way also.  I am just wondering if anyone knows why this would be happening.

Thanks