If you have the TV connected to the headphones port at the same time as trying to get sound on the laptop speakers, you won't since it'd mute it from the onboard speakers.
I assume you know that though, so i'll think that you've dissconnected that, and now have no sound.
Have you checked the sound volume icon int he taskbar on the bottom right? If you click that, check that the level is up, and right click this, and go to Open Volume Control
Check that none are muted.
I hope this helps, and its a weird problem...