Computer wakes itself from sleep mode...

...when I turn off some separate switch in another part of the room.

Okay, in the evening when I'm done using the computer, I put it into sleep mode. Sometime later I will turn off the power to some other device in the room. And the computer will come back on at the same time.

Obviously some electrical noise or surge from the switch is causing this, but I'm not clear on how the computer is tripped awake. Perhaps my wireless mouse. lots of testing to do, but if you had this problem, what resolved it?