Does the resolution set of the PS3 make any difference?
There is a rather bizar ritual to reset HDCP between the devices.
Unplug everything for an extended period of time.
Plug it back in and bring up display first putting it on the proper input, then the AVR once again putting it on the proper input, and then the source.
If this fixes it? be prepared as it will most likely do it again. Take care when switching sources to minimize issue.
Switching sources while content is running is one way this sort of thing can happen.