There are issues with the power saving facility SKY use,whereby your box turns itself off overnight. Also, the settings on the Bvis 7 for "follow TV", "Never", "after 30 minutes" etc can conflict with timer recordings on the hard drive and also with the scart control voltage ( if you still have scart connected - you could be using phono's )
In effect, its possible to end up with your TV and box mixed up,and the on command,which the TV sends turns the box off - nmeaning you dont see anything. pressing menu 1 or menu go go ( depending on exactly why your boix and TV are out of sync ) usually gets the box back on in a few seconds.
Other possibility is a misplaced IR emitter - if its not quite in the right place you can get interittant issues - sometimes light dependant. Or maybe even a low output diode in the emitter.
But your description suggests the IR is in fact in place and OK,but there is a clash a initially described.
Hope this helps.
Bang & Olufsen of King Street - Manchester,UK. SKYPE - beokingstreet