Is this overheating?

[Heresy]

I have had a problem several times now where the video on my PS3 cuts out for a few seconds then comes back on (my TV shows lost signal and goes black then comes back); it keeps going on over and over until I turn the system off for a while. It only seems to happen when I have been playing for a while but I haven't seen anyone describe this symptom of overheating (it's usually described as games freezing or the PS3 powering off with a red blinking power light.) If I turn off the system and come back an hour or so later everything seems OK and I am able to play with no problems. It also seems inconsistent on when it happens; I'll play Tiger Woods or F1 for 2-3 hours and have no problems and then sometimes, like tonight, after about an hour of TW it happened. It also doesn't just happen during games; once after playing for a while I was looking at the PS store before I logged off and it happened there (it also happened before and after 1.6 so it's not something new with that patch.)

I did have the unit in my TV stand with 6" of ventilation all around but it was on a glass shelf above my receiver so the bottom was fairly hot. Now I have moved it off to the side of my stand and set it on its side with the vents pointing up to see if this will keep this from happening. Just wondering if anyone has seen this before.