Anti-Theft Problem
 

I have a 2000 XLT, 5.0, AWD, AT, and every now and then (especially Monday mornings), my Explorer will not start. The "THEFT" light on the instrument cluster will flash quickly, the car will try to start, but it just can't make it. I'm not sure what to do, I don't want to mess with anything because of all the computers. The one thing I'm thinking is, could it be because I've missed and oil change. I've had the truck almost 2 years now and never missed an oil change, until now. I used to have a 93 Crown Vic that wouldn't start if I didn't change the oil at the right intervals, but I just don't know. Thanks for your help,
Justin