I think I screwed myself by buying a 3rd party chinese cable.... I have a late 2012 iMac. I bought an external monitor yesterday (Asus VG248QE). I bought a mini displayport to displayport cable so that I can use the monitor at 144hz. The cable is QVS 6.5ft model #MDPDP-2M from Microcenter for $15.99. It was working fine yesterday. I wanted to have a more permanent set up so today I unplugged everything so that I can use both monitors comfortably. These are exact steps: 1) plugged in ASUS monitor power to wall. 2) plugged in ASUS monitor to imac. 3) plugged in imac power to wall. The power socket started sparking up and the thunderbolt port also sparked up. This happened for a good 1-2 seconds (however long it is natural reaction to pull out plug). I'm considering what my next steps should be... BTW the iMac turns on and loads but it makes a flickering sound and smells so I'm keeping it turned off. pictures coming soon.