What are your export settngs?
Where are you seeing these black borders? Player?
Are there still black borders if importing this file back into elements on the timeline?
I've tried many export formats, but my go-to is usually the default wmv settings with height and width adjusted to 1920x1080 (although the black borders appear with 720x480 as well)
The borders appear on all four sides of the video in Windows Media Player, VLC Player, and Elements Organizer.
The borders still appear when the file is imported back into the timeline.
The output settings you're using have the Aspect set to DV/Widescreen.
Don't know how much of a difference it will make, but try setting it to 1.0 Square Pixels.
Or better yet, try Publish & Share/Computer/AVCHD with the preset for YouTube HD.
The YouTube HD export setting did the trick. Thank you so much for the help!