One problem related to transmission not go into gear has been reported for the 1999 Lexus RX. The most recently reported issues are listed below.
1999 Lexus Rx300 awd, transmission failed while driving on the highway at speed limit of 75 mph. Transmission went in to neutral, and created a serious driving hazard that required maneuvering through traffic with no control to get off the highway. The transmission would not go back in to gear and there was no way to control the speed of the car.