2000 Bravada cold weather starting issues

Whenever the weather hits about 30 degrees or less, my Bravada does some wacky things. When I turn the key, the dashlights will be completely off. As I attempt to start it, the dashlights will flick on and off for various periods of time. It is only when they flick on that it will even try to start. Any suggestions would help-I've had new plugs and a distributor and a new cold weather start sensor installed and the problem persists. I've put over $5,000 into this vehicle not counting items covered by waranty. My 2000 is mostly a 2006 with all the new parts on it and still it acts up.:banghead:

If the starter doesn't spin the motor real good, the battery may be weak.