just upgraded my 2009 iMac to a new 2013 model (3.5 i7 w/ gtx 780m). guild wars 2 ran OK on my old box on mostly low settings. its runs great on the new box except for one annoying issue. at what appears to be random times- the fans kick up to full blast. i've watched the CPU and temperatures and do not see any corresponding spikes. even on low graphics settings it happens. is this normal behavior for a high end card or did i get a lemon? any help/suggestions would be greatly appreciated!