I have the white 250Gb Final Fantasy Xbox 360. I use it with an HDMI cable running at 1080P. After the latest update the screen now randomly shows black lines and is fuzzy with greeen and purple dots on the screen. Sound is also patchy. I have tried all the resets mentioned in here I think. Tried 2 new HDMI cables. If I switch to 720P or lower all works fine with no issues at all. Why would this happen please and is there any way to fix it?