Display Problem: Philips LED TV

Hi Model - Philips 46PFL7705D/F7B. Description - 46" Class LED 1080p 120Hz HDTV. Problem : Display not appearing(not even Philips logo) This happened right when i was watching my TV that was connected to the Laptop through a serial cable. While watching the picture froze and the display never came back. Seems to me that audio is still there as i can hear it when i connect it to Laptop. _What I have done to Troubleshoot_