This happened to mine, and the same exact symptoms too. Game froze while loading something from the disc (presumably) and I switched it off in the back. Apparently that's a no-no; you never risk this unless you absolutely have to. It can sometimes burn out the lens.
After this, my PS3 wouldn't read anything; games, movies, cds... it only worked while reading stuff off the HD. It would work for awhile if I had the system off for an extended period of time, but would later cause the game to freeze and cease to read anything else off the disc.
I wish there was a way around this to prevent this. Sucks that some shoddy programming can indirectly cause a system to short by forcing the user to switch the system off in the back in case a game completely locks up the PS3.
Try the reformatting trick, but don't hold your breath. See if you can sell it to someone on eBay (always a good amount of people out there who like to gut systems or revive broken ones). Use that money to buy a new PS3 slim.