Most annoying thing ever. I bought a brand new GTAV bundle yesterday, and was going through all the setup process, and when I got to the "Enter Account Name" part, the Triangle was being automatically pressed like 5-6 times a second. I thought that maybe because the controller had like 2% battery life that maybe it was having issues because of that. I finished the setup process, let it charge for a few hours, and tried it again. It was still being pressed automatically, but not as bad. Maybe it would work fine in-game. So plopped in GTAV, and was playing, but when you get to the getaway car at the intro level thing, I couldn't get in the car. Now triangle doesn't work at all. Tap the PS button to bring up the XMB to check Device Settings, but I can't navigate the XMB. I hold the PS button and exit game that way, now I can navigate the normal XMB, but Triangle still doesn't work. I formatted the PS3, thinking there might've been a bad codec on it, and this would solve the problem, still didn't fix it. This is really frustrating because I've owned PS3s from day one release date and never had an issue.
If you have already tried to reset the controller by sticking a paper clip clip in the little hole on the bottom of the controller and pushing in a few times and that don't work, then take the controller apart and clean it. Otherwise, time for a new controller I guess.
I've reset the controller about a dozen times. I would normally guess the controller, but I find it a bit odd that other than the Triangle, it works fine during gamelpay, but then wont work at all with the in-game XMB up. And the controller is a day old, so I wouldn't imagine it needing to be cleaned.
I have a roomate with a PS3. When he gets back, I'm gonna sync my controller to his PS3, and see if it still acts this way.