I just experienced that a recent update from Apple rendered my bluetooth functionality completely dead. The status bar icon was greyed out with a horizontal lightning bolt looking icon crossed through it.
After some time on Google, i find i am not the only one
Solutions listed below worked like a charm..
Another solution for a Intel based Macbook Pro..
1. shut down the computer.
2. remove power cord.
3. press the power button for 5 sec.
4. connect the power cord.