^Ha ha.

Thermal interface material aka thermal paste aka goop. By any chance did you reseat your heatsink after you removed it? Your 1 yr old goop whichc ame with the Intel heatsink is no good after a brief period of usage. And during the course of your dusting inside the enclosure, dust must have settled atop the goop which negates any effect of heat being conducted to the heatsink from the IHS (Internal heat spreader - the copper plate atop the cpu!).

Buy a tube of a TIM - MX2, TX2 or MX3. Drop a rice grain worth TIM atop the IHS and reseat the heatsink.