What happens if you take the HDMI from the PS3 and plug it into your TV? If this works, then you have something setup wrong on your amp. If it doesn't work on your TV, then you don't have something setup correctly on your PS3. Don't forget that when you are in your setup PS3's setup menu for audio, and you select "HDMI", you need to keep scrolling to the right with the arrow button to get to the screen that allows you to save the changes.
I currently own a 40gb PS3,a Harmon Kardon AVR 146 and a Samsung 56" Slim DLP. I have my PS3 run into the amp with an HDMI cable and another HDMI into my TV. When I switch the AMP to HDMI input it is not broadcasting in surround. I checked the settings on the PS3 and everything is set to HDMI, however, still no surround. Does anyone have any suggestions that might help me solve this problem? I appreciate the help.