Maybe a little late to reply, but I'm facing the exact same problem with the same machine. I've had the laptop for more than two years before I first started using a second screen about a year ago and faced the above mentioned problem. As suggested by tech support, I cleaned the fan, reinstalled Windows a couple of times, did all kinds of diagnostics and checks, bios is the latest available (A11)... nothing to report. Today I fitted a new fan and heatsink, that didn't help either. Really frustrating.

Is there going to be any kind of reply from a Dell technician?