A couple things. Make sure there is a good ground on the cable service coming into the house, I have seen that cause weird issues. Also try a HDMI reconditioner, like the Key Digital FIX-22. I had a customer with a Canadian satellite receiver and it had a similar issue, but it would work for about 5 minutes then the sat receiver would completely lock up. I put in the FIX-22 and it has been clear sailing ever since. The customer got several sat receivers and they all did the same thing, not a defective box but some incompatibility between the receiver and the balun.

Good luck.