Pontiac Repair: Key turns but no sound, fuse boxes, pontiac grand prix

Question
On my 2000 Pontiac Grand Prix GT, I turn the key in the ignition and the insturment lights come on like normal but there is no sound for the engine, no cranking, total silence. I have tried other keyes, using the shift lock release, the car computer says nothing, i had a tune up back in october and changed the battery, and oil filter gets changed like clock work or milage. The car has about 115,000 miles. The problem started in december and it has been on and off since. After several tries it starts back up just fine like nothing happens. One time it was not moving for so long that people tried to jump me and it didn't work. The towing guy tested the altinator and the battery and said it works just fine. If you have any ideas that would be great. Oh and my car does have the anti-theft system installed.

Answer
ok well what seems to happen is the anti theft fails to read the key and thus wont turn over,,look at all the fuses, both fuse boxes i think one is on the right  pass side end of dash, check the bcm and securty fuses... then you can turn your ignition into the run postiton and let it sit there with the key turned in the run rfor thirty minutes, im sure you have tryed to start it wiggling the shifter from drive to neutral. if that doesn t work im afraid your ingnituion is not reading the key and will ahve to be replaced and or the bcm   body controll module thankyou