2003 Taurus starting problem

I have a 2003 Taurus that has just started to have a problem starting sometimes. It may go 2 or 3 weeks before this happens again. When we turn the key it does nothing. The security light doesn't blink, all the other console lights come on, I can hear the fuel pump. Battery is in good shape. When this has happened we have tried changing keys. That didn't work. Most of the time we can try it again after 5 mins. and it starts fine. The last time this happened it was about 30 mins. before it would start. Does anyone know what could be causing this and/or what I can do to repair it ?
Thanks,
Tanis76

Make sure the battery connections are tight and clean. If they are, then there may be a problem with the factory security system. Being an '03 are you still under warranty??

I had the same problem with my 2003 taurus approximately a month ago, it happened once, and I ended up jumping the car, and it started after about 15 minutes, the second time it happened, we tried everything and it wouldn't start. we checked the battery, checked the fuses. We ended up getting it started when we wiggled the starter wire ( black coiled wire connected to the starter) We brought it to the dealership and they ended up hooking it up tighter, and the car runs fine now. Mine wasn't under warranty and ended up costing approximately 70 because they had to diagnose something when I already told them the problem.