Can't get Domain Mapping to work

When I try to enable domain mapping for one of my sites,, to map the domain, the domain mapping tool just "hangs" with a never-ending spinning disk. I've tried it multiple times. I have added to both local and global DNS, and checked to make sure that resolves correctly. I've also added the to the apache config for this site. I have deactivated most other plugins to assure minimal conflicts. It is still hanging. Can you help?