Problem with Sky HD

[buttons77]

Hi,
I have just got another Sky HD box because of problems with the previous one but there are some HD channels I can't watch - BBC HD, SyFy HD and LuxeTV HD - the sound is ok and I can hear the programme bit the screen is just blue. All other HD channels are great.
Is there some code I need to enter to get these three channels or am I going to have to get into more phone calls to Sky (it's taken 6 months to get them to change the box in the first place!!)
Hope someone can help me.

[AlBags]

Check signal strength and quality first.
Check all connections .. HDMI or Component (whichever of the two you are using)