yamaha 1067 hdmi signal loss

hello i have a 1067 amp and am losing the picture on sky but still get sound when the amp is on. In standby mode i loose sound and picture. the only way to get it back is by rebooting sky but if i connect sky direct it doesnt seem to happen. ive even put a new hdmi cable between the amp and tv. I just wondered if it could be a problem with the hdmi board on the amp because i need to get it sorted before the guarantee is up on the amp