Well if it's only in a couple of games then it does sound more like a programming error than a hardware error, but one can never be sure I suppose. At least with Black Ops you know for sure, but if Angry Birds is the only unexplained issue, then maybe there is a bug in it (or a corrupted file, though usually that would be more noticeable like when computing scores or something, but sometimes it is random, redownloading the game may help). I had Minecraft do terrible things before (when Notch forgot to remove the gamma code, silly him), but I don't think it ever locked up my computer thankfully.
As I said, I don't know much of anything about the PS3 as I don't own one, but it's just a over specialized computer so I can only take what I know of computers and apply it to the console. It definitely would be a good idea to see if they would know or perhaps bring it to the official Sony website (support section and forums), of course an initial search will either get you an answer or force you to question them.