Hi reid.gould,
as JGerth told, it should be some kind of track left behind by an Autocad vertical.
As a workaround, try to save your file in dxf format, no matter which release.
Then open it and try to do purge now.
Should delete everything.
By the way, there are thousands of "Registered Apps" in your dwg: try "-purge" command from the command line, with the "r" option.
Should get rid of all those registered apps.
Hope this helps,
Giancarlo
