imac tv wifi problem

I have connected my iMac(mid 2007) to my tv with a hdmi cable. Problem is, when I watch a movie or something on my tv from my iMac, my mac loses its wifi connection and it wont restore itself when I turn the tv of. I have to turn of the wifi on my mac and tunr it back on.

I would like to be able to use the internet while watching a movie.