thanks for your response.
judging by how no one else seemed to have this issue, i figured there was something else interfering with the ubercart core modules. i did a clean ubercart install with no other modules or themes and editing orders worked fine. i isolated it to one of the functions in my theme's template.php. i commented that out and everything works fine.
you might want to check if you're still having the double-save on a clean install before editing uc_order.admin.inc