Using HDMI input from the PS3 for game play should work. I suspect you had a type of HDMI handshake failure that OPPO is working to fix in the next firmware release -- a failure of the Copy Protection check. If it happens again, see if you can use the Input button on the OPPO remote to switch the OPPO back to Blu-ray Player, then select the HDMI Input again. That will force a new HDMI handshake and may clear the problem.
That said, I would not recommend using the PS3 through the OPPO for game play. The PS3 games are authored to use video in the RGB video data format flavor which OPPO calls RGB PC Level, but there is currently no way to configure the HDMI Input on the OPPO as to whether RGB format input should be treated as RGB Video Level (the default) or RGB PC Level. In addition, there is currently a bug which results in incorrect "color space math" if RGB input comes in at HD resolutions.
For movie playback on the PS3 (including Netflix), the PS3 uses YCbCr 4:4:4 output by default, and that works without problems through the OPPO input. Although you can set movie output on the PS3 to either format, game output typically "forces" the PS3 to RGB output.
Bob- Thanks for the information. I will look into another approach to keep the PS3 in my system. Also, thanks for taking the time to share your product knowledge with this forum. Your posts have been most informative.