Problems with Anynet+ and AV-receiver

[TOMillr]

I'm having troubles getting HDMI-CEC/Anynet+ to work properly with my setup (C6000 TV, Pioneer VSX-S500, a Blu-Ray Player and settop-box).

Whenever I turn on the BR-player or settop-box, the av-receiver and the tv are turned on automatically and switched to the proper hdmi-input on both devices. So far, this is how it should work.

Unfortunately, once the TV has switched over to the corresponding HDMI1 input (to which the av-receiver is connected), the TV somehow forces the receiver to switch the audio input back to the TV sound instead of the input coming from the BR-player/settop-box.

This is really annoying, because I then have to manually switch back to the proper input on the av-receiver just to get my picture and audio back. Is there a way to prevent this?