Our electric ac/heat unit for our house suddenly stopped working the other day. The outside unit still comes on(spins) when the heat is turned on, but the inside unit does not. When it is turned on, you can usually hear it start to crank up, nut now, nothing. What could cause this?

Check at your panel to see if you are still getting 240 vac from your provider or just 120. Consult an electrician if you have never done anything like this before.