This post is for all that Googles for this problem with PS3.
Replacing my AppleTV with a PS3 gave me a surprise, connecting the PS3 to the existing HDMI cable used for the AppleTV gave me the flickering issue.
The PS3 was actually a 320GB version used in the house for a year on several TV without issues.
Now, on my Sony KDL-60LX900, flickering was regular, in irregular intervals. I tried several tricks settings inb the PS3 as fixed resolution, no HDMI control etc - nothing working. Between the PS3 is a Marantz SR5006 reciever, that I suspected as the source of the issue.
To make it short, as several Google's searchs reported, the HDMI cable was the issue it seems - the cable that worked flawlessly on the AppleTV...
Replacing the between the PS3 and my Marantz SR5006 has solved the issue (for now, anyway ... )