By not having a battery back-up when you disconnected the battery, you might have inadvertently erased vital info that the ECM would use to start and run the car. That's just my guess. You may have to bring it to the dealer.
I have taken out battery few times nothing happened but if you could tell us what happens when you try to turn on the ignition
The battery you are using is properly charged
if yes i think you have lost a ground connection or something
try explaining in details the experts in the forum will be around one time or the other they can help you better if you give more details
ok try this one if the car will crank. turn key to run postion do not start it leave for three minutes then turn key off. then back on and leave running for 30 seconds or more. I got this out of my 99 catera manuel. it says to do this anytime of a power loss to let the electronic throttle control cycle to find its home postion maybe this will help you. oh yeah section 6-29 in my book.