HD screen

Question

Hi i have olevia lt37hvs more then 1 year now(no problems in this time) But from like 2 days ago i have problem with Hd channels. A am using HD antenna, sometimes works an fiew hours and next time 1 min. I am getting loud noise and screen its mix of color pixels. After that i need to turn off tv to fixed. When i am using Normal channels, dvd, or computer i dont have this problem( Just HD channels). Plz help