you may have your park interlock malfunctioning, this is a pink plastic device that will disengaged when the brake pedal is pressed. This is known to fail, by the small spring in the inside breaks. I believe that there is a recall on this lockout device, but this is (before) it fails. Typically, it's a $500 repair at the dealership for a $14 repair kit. There are many videos on YouTube, explaining this problem and a possible temporary fix.
〉 Answered on Aug 21st, 2012 by Amanda J. Pierce, MBA "AJ", Certified Mechanic, Project Coordinator; Primavera Scheduler at VIGOR Alaska Industrial Shipyard & BizzM3ch Solutions
It could be a problem with your brake switch. Since you have to push on the brake before you move your lever, if this switch is inoperative, it will keep you from moving the shifter.
Look in your owner's manual to see if there is a place to put your key to allow you to manually override the brake pedal so that you can move the shifter into gear. Most vehicles have this.
〉 Answered on Aug 21st, 2012 by Lori Johnson, Owner and Instructor at Ladies Start Your Engines