I have the problem with the ps3 as well, my amp sometimes goes crazy after switching to the ps3. It keeps cycling through sound formats as if the 2 systems can't agree on what to use. Switching to another input and back always fixes it.
Probably a HDMI handshake problem. HDMI can be quite finicky, when switching back to tv my cable box sometimes complains about HDCP secure link lost for 2 seconds or so.