Since you are in the US, like me, i think you should check your prem project settings, sounds like something my friend was doing. I checked his out for the very same project, and he had his project set at PAL, and he was using NTSC footage, which Pal has more lines, therefore creating dead space. If it is not doing that on your editing, but only on export, you may be exporting as pal.
Mac G5 workstation with 4 gigs of ram, 4x250 gig drives in raid 5. High availability cluster server running centos for a server. 2xCanon GL2 cameras.