(adsbygoogle = window.adsbygoogle || []).push({}); How I got mine: Halfway through a game in MW3, my ps3 freezes. I shut it off, and turn it back on. When it turned on, the YLOD started happening.
Also, before I played MW3, I tried to install DC universe online, but I wouldnt install because I didnt have enough space in my hard drive. Could that be one cause?

either faulty hardware, overheated system or your power supply is messed up.

It either means the PS3 is over heating or there is some kind of hardware fault.

Thou, in your case, it seems like what happened to my old PS3, it overheats to it's max temperature, then shuts down and cools right down to room temperature. In this heating/cooling process, one of the processors may not have set back onto the motherboard properly. This is most likely why you're now experiencing a YLOD.

Reflowing CAN help, but I wouldn't particularly recommend it, as it will only last for a while, and can end up doing more damage to the system. However, reflowing your system could potentially give you enough time to switch it on and grab all your save data etc, if that's what you were looking to do.