You can also select all the faces of the object, then Edit->Detach Faces (or shift+d). This will detach all of the faces and put it in a new mesh in the same location, with the center reset. You'll have to delete the old, invisible object afterwards (use the List Items button in the top row of buttons).
Or, you can edit the file in notepad or another text editor.
Replace (the origin values will be different for you)
pivot {
origin { (-21.292 17.327 0) }
}
With
pivot {
origin { (0 0 0) }
}