I changed the bulb of one headlight and now my 2006 Saturn Vue won't start.

does it crank (turn over ) ? are the batt. terminals tight ? do you have spark ,fuel pressure ?

Yes, there is juice to the battery, it turns over but will not "catch" to start the car. The battery was an expensive one and is only 6 months old. We tried several different instructions that were supposed to disable the security system, but nothing worked. We disconnected the battery for a while and then reconnected it, but that didn't work. The battery connections are tight. Can't tell about spark or fuel pressure but they should be fine. The Saturn was recently gone over quite thoroughly by a mechanic here but he was closed today. I bought it used and it had a ton wrong with it, but everything obvious has been fixed. It was running great before we replaced the headlight bulb! Do you think it is the security system preventing the car from starting? If so, do you have any other suggestions for disabling it? Thank you so much.