SD not in from of me but I bet you have to delete all attributes inside the object before you can delete it. Surprised you can't rename it. Most things in Service Desk linked via GUIDS so name means nothing. Wonder if you could just change it in SQL. You could also just restore your previous DB from the night before.
Make sure that the object is not currently in use anywhere and that the "Is Knowledgeable" is not set. I've seen it before where if the "Is Knowledgeable" is set to true, you cannot delete it.
tried to clear the object and all its attributes out using different queries but it would not clear all of the way.
so we just restored our previous DB from the night before