Mountain Lion may have a bug that's affecting users who have the Auto Proxy Discovery and Automatic Proxy Configuration networking features turned on, says Daniel Jalkut of Red Sweater.
According to Jalkut, apps, like his own MarsEdit, throw an error involving the CoreSchedulingSet or EmptyCoreSchedulingSet C++ objects when trying to connect to some network resources.
Working with the folks from Agile Bits, Jalkut traced the problem to the Auto Proxy Discovery and Automatic Proxy Configuration settings in the Network preference pane. Under most circumstances, these opti
