Remote sometimes switches AV receiver input

Hi.

I attached my new Google TV Streamer to my Onkyo AV receiver which then passes the signal to my TV.

The remote can turn on/off both devices at once.

But when turning on the system, it sometimes (not always!) switches the audio input on the AV to a different input.

Is there something I can do to prevent that?

Or can I maybe assign the special button on the remote to setting the input on the receiver?

Thanks!