Help Starting Issue. Doesn't want to start sometimes

I have a 2000 intrigue and I have a huge issue. My car will start sometimes and then it won't start other times. I replaced the ignition cylinder, the pig tail coming off of the cylinder, I tried a new battery, and I had the new ignition cylinder programmed to the car by the dealer but I told them I would put everything back together so the car ran perfectly and I went home and put everything back together including the radio and such and it stopped working again. I don't have any other clue on what is going on with this car. Could it have something to do with the radio? Any suggestions please let me know.

Are there any lights illuminating on the dash? How does the car run when it does start? Check the battery cables for corrosion and wear. When it won't start, what sounds does it make? Is there a clicking sound like a dead battery or does it just keep turning over and not catching/ When you turn the key to the "on" position, do you hear a light hum which is the fuel pump being primed?

Reason I am asking all these questions is to try and determine if this is an ignition problem or fuel problem. Once we determine this, others with more knowledge then I can help.

The theft light does flash after it doesnt start but otherwise all the normal lights come on when they are suppose to. The starter doesn't turn ovwe at all and makes no sound. The fuel pump does engage and you can hear it running. The battery terminals look fine. This is definately a passlock issue I just don't know what to do I haven't been able to use my car for such a long time because it works and then doesn't work. And thanks for the response. Do you or does anyone else know how I can fix this issue?

The actual ignition cylinder was replaced? Or the ignition switch?

There is the possibility it wasnt programmed right.

I replaced the lock cylinder and the lock switch and it was programmed by a chevy dealer. The car worked for a couple of hours and then started doing the same thing again. Work and then Don't Work. Work and then Don't Work. It makes no sense to me. I have tried everything and the car seems like it works and then a couple hours later or a couple days later it does the same thing.:banghead: