Engines stuck at 47.2% after landing / nose wheel steering failure?

A very strange thing happened on my last flight today. I landed at KLAX with a perfectly normal landing. When I went to taxi off the runway I noticed my nosewheel sterring was not working and my power was stuck at 47.2%...autothrottle was off, autopilot was off. The throttle was locked in place and using either the keyboard or my saitek throttle quadrant would not move the throttle in any direction. I then did a normal engine shut down procedure and the engines kept running at 47.2% and would not shut down. Chad