What would cause the steering wheel to make a pop sound and then no longer turn the wheels and air bag light start to flash?

What would cause the steering wheel to make a pop sound and then no longer turn the wheels and air bag light start to flash?
The symptoms that you are describing lead me to believe that you have a failed "clockspring". The clockspring is a mechanism that is attached behind the steering wheel. Its purpose is to provide electrical connection to the driver's airbag. Being that the steering wheel is a rotating object which houses the airbag, the clockspring is a sophisticated mechanism that maintains electrical connection regardless of the steering wheel's angle. If the clockspring were to break, it could cause the popping noise that you heard. Depending on the breakage that occurred, it could obstruct the turning of the steering wheel. Additionally, since the electrical contact to the airbag is now lost, the airbag warning light flashes to alert you to the malfunction.