I just wanted to say thanks for the extremely helpful information in this thread.
I recently (few days ago) purchased a Samsung PN50C680. At first I thought it was a setting some place, but later realised that the sync between the glasses and the TV was degrading, and then coming back, or at times would even reverse the Left and Right Images (had to 'Image Correction' to fix).
I was watching 'Open Season 3D' and paused the movie. For about 1 minute everything was fine, and then suddenly the screen view would dim gradually, and 3D effects would disappear into a 2 image blur. Both sets of glasses did the same thing. I could simply hit the power button on the glasses, and everything would be great for 30 seconds to 10 min. until the sync started to degrade again.
I called Samsung, and they wanted to send a tech out, which I agreed to. The rep felt the issue was also with the IR system. I went to work, and put Google to the test. After reading this thread, and the work night done, I headed home with some troubleshooting on the agenda.
I Reset the TV by holding down the 'Exit' button for 10 seconds. I used my cell phone camera to look and make sure the IR transmitter on the TV was working (it was). I then, took a roll of Electrical Tape, and used a Mechanical Pencil to poke a hole in the tape (I used a .5mm lead size pencil with the metal tip, and simply poked it into the whole roll of tape). I cut the tape so the hole was right in the middle and placed it over the IR sensor on the Glasses. With a tiny bit of stretch, just enough to keep the hole open (smack in the middle of the sensor), and the tape nice and snug to the sensor, I gave it another try.
I fired up the TV 3D, and hit the power button on the glasses. The glasses turned on (which they wouldn't if IR was completely blocked), and watched for awhile. Not once in 3 hours did the glasses drop sync, get confused, or try to flip images. I popped in CoD: Black Ops, and I suddenly loved my PS3 all over again. Since the tape, I haven't had one issue. Now, when I look away from the TV, the glasses turn off and I can see without the blinky effect. If I look back at the TV within a few seconds, they turn back on, and go right back into crystal clear 3D.
I was just about to return the TV and go with a Panasonic (which weren't in stock and I would have had to wait for 2 weeks), when I ran across this thread. Thanks for posting your info. Saved me a bunch of money!