Ps3 HDMI problem

Yesterday I was playing gta 4 on my ps3 and it works perfectly in hd and today I change HDMI cable and it's not in hd no longer so I change cable back and try do same thing I was doing last time when hdmi was not working but it didn't work out I stuck when have to choose or 720p 1080p 1080i and 576p I try all combinations and it's shows me black screen fo 30 sec. Please help.