Coolermaster probably used cheap LED bulbs in the mouse. Cheaper bulbs are not as efficient and will use more power and thus generate more heat in the conversion of electrical energy to light energy. Add to that the fact that the mouse is covered with a thin film of rubber to increase grip, and you have an "insulation" effect trapping the heat from the bulbs. All of this is hypothesis but makes sense to me. I don't see any problem from this. Frag on...