I have a 2000 3.5RL, when I tried to start the car, it cranks but doesn't start. Someone helped me jump start the car on Friday evening, I drove home fine. Sunday morning, I tried to start the car, same symptom, I jump started it myself and test drive it for about 20 miles (I didn't stop the car). However as I pulled it into the garage, it died. Then I tried to jump start again, it won't start anymore. Now, the gear is locked and I could not even set it to neutral.
Anyone had the same experience? What could be the cause? I need your suggestions.

 

Could be your battery. Could be your main relay. Do a search on main relay and see if the symptoms match what you are describing. Good luck.

 

I had a similar problem, but I didn't try a jump start. I figured out it was the main relay, and I replaced it myself in about 15 minutes. It's under the dash.

 

Hope you got running again by now...
If you haven't...does the green key light up? It is one of the indicators that turn on once you insert the ignition key. If it does not light up, most likely it is the Main Relay module.
It happened to me and opening the module box and re-soldering all the tips (as suggested in these forums) took care of it. Saved me $50.