Do you manually switch back and forth between TV and monitor or is there some automatic detection going on? Some programs, like games or video players, will initiate a graphics mode specific to the type of monitor you're using. So, for instance, if you have a video player like Windows Media Player running while your video card is set to run output to the monitor, trying to switch to the TV may cause problems (on my computer it simply will not let you switch while the player is running. I've never had it freeze up though). If your system switches between TV and monitor automatically, or if you have cloning going on, that could be what triggers the freeze. So, my suggestion is that you close all video-oriented programs before turning your TV back on and see if that prevents the freezing.