Lenovo T60 interfacing with Vizio HDTV using RGB...

Question

I am having trouble interfacing my Lenovo T60 with ATI X1400 graphics card to my Vizio 50" Plasma HDTV (1366*768 resolution) using RGB cable. After 3-4 minutes of displaying properly on TV, TV report no signal and the picture moves to the laptop lcd screen. Many times picture keeps flpping between HDTV and Laptop screens and sometime laptop crashes.I have similar troubles connecting this laptop to a 24" monitor @ 1920X1200 resolution.