Sky HD + Box freezes after start up

[Skyaintcheap]

 Everytime I switch on my Sky + box works fine for between 2 and 5 minuites. The picture then appears to almost double in size and freezes with a yellow line at the top of the screen. The audio continues (live or playback).  If I unplug the box and reboot I get just the audio but in 3 second bursts and no picture. I then repeat the process two more times and it works fine for the rest of the evening. This happens everytime I switch on.  Any suggestions or is it time to say goodbye to it, and possibly sky?

Thank you.

[caesarome]

You could try a planner rebuild:

Press Services on your remote

Select Help

Select Sky+ Rebuild

This should take no longer than 10 minutes, don't do it if you are recording or due to start recording something.

[Skyaintcheap]

Thank you but no joy. Same problem immediately after rebuilding.