there could be as few reasons.... CEC turned on somewhere.... eg if you have that turned on ...on nay devices it can mean eg if you hit open on disc tray of blu-ray player ... processor will switch on...
otherwise possible there is IR code conflict ? something else has an on code similar ? or again cec related ?
anyways first things id do is switch off CEC on everything. not there are different names for this in various devices ... eg viera link for panasonic and such...