Double Vision for my Hitachi 57swx20b?

Hi, i just purchased a Hitachi 57swx20b for 400 dollars. the guy said it was in perfect working condition. I turned it on this morning and it was fine, clear as a bell on HDTV. After about 2 mins of watching it became blurry, like it's outlined with green and purple haze. like double vision almost. you can make out the picture and the sound is ok. I'm just not sure what the problem is.