I decided to share this information, since I have seen at least three other people being affected by it as well.
I had recently replaced my PN63C8000 with a new one because of this issue. It would lose sync during 3D playback at random times. Well, it finally arrived a few days ago and the new one loses sync as well. I was mega frustrated because I really like the Samsung, but the 3D losing sync at random times was killing me. When it loses sync, it flickers and appears for just a second as though the glasses turned off. I had tested different lighting, no lights at all, replaced my hdmi cables, the 3D glasses, the whole tv. Nothing worked. It had to be something causing this issue. So I decided to do a bunch of experimenting this week. I eventually found that bright flashes on the screen were causing it to happen. I then noticed that the bright flashes were possibly reflecting too much light on the small IR sensor in the front of the 3D glasses. Eventually it led me to place my finger over the small sensor on the front of the glasses and see if it would lose sync. I tested this with the animated movie "9", which later in the movie a giant snake-like creature has flashing eyes similar to a strobe effect. My glasses would normally lose sync like crazy on this part. It's a perfect test. With my finger raised over my head and covering the sensor, it would not lose sync whatsoever. I tested it over and over, both ways, with and without, and it never lost sync with my finger covering it. Very strange.
I decided to try tinting the sensor a little, so I took a tiny piece of Scotch tape and covered it, and it still happened. I put another piece on top of that one and it still lost sync. I took a Sharpee and colored over the tape. No go. I next took a piece of electrical tape and covered the small IR sensor on the front of the glasses. Believe it or not, this actually worked! I was not able to get the signal to lose sync whatsoever. I tried a bunch of 3D games and some movies, and none of it drops sync now. I know it's lame that I even had to resort to doing something like this to get such an expensive tv to work correctly, but aside from this, I really love the TV. My tv is kept in a very dark and small living room, and at 63" the flashes of light are quite bright. Perhaps that is the cause, who knows. If you decide to put tape on your glasses, it is important make sure it's just a tiny piece that covers most of the IR sensor. Not all of it, but most. I noticed if I covered all of it with electrical tape it would lose signal completely. So make sure it's just a tiny piece that covers 97-98% of the sensor. I tested this on both of my 3D glasses and it works perfect on both. A few days have passed now and I haven't had one drop in losing sync. I play a lot of PC games in 3D on it using the IZ3D drivers and haven't had any issues since. It's really nice to finally be able to enjoy all kinds of 3D material the correct way.