I have a sunroom in my house with 1 light and 1 outlet/light switch. The problem is every time I plug in t.v. and turn it on the light will flash on/off only when the light is on, but if the light is off the t.v. will work fine

I would check tightness of connections in box with switches.

Does the light flash off then on or does it dim then go back to normal? Has this always happened or did it just start? If it is a new problem take strat's advice and check connections. If it always happened the circuit could be reaching max capacity.