part/assembly relations

I am using Wildfire 5 with Windchill. I started a project using 'dummy' part numbers since nothing had been assigned yet. I created several parts and an assembly. When the part numbers were assigned I renamed them in Wildfire. I had all the parts and the assembly open when I renamed them. For some reason it appears that two of the parts did not rename but created new parts with the new part numbers. When I did this I made sure that it was 'rename' not 'copy' being done. I removed the old parts and added the new parts to the assembly. When I try to remove the old parts from the work space it will not delete unless I delete the assembly. How do I break this relation so that I can get rid of these old parts?