Something very strange just happened. I have a multisite installation with Pro Sites and the Domain Mapping plugins installed (all other plugins are disabled).
Everything was working fine then all of a sudden when trying to access the admin panel for any website with a mapped domain caused a php script time out (30 seconds). The actual website frontend works fine and all the features etc are working. It's just when I access the admin panel for a website.
Note that accessing the Network admin panel works just fine. Also, I can get back into the admin panel if I either disable the plugin or empty the domain_mapping table.
I'm using WP 3.4.1 with domain mapping 3.0.7