High transverse momentum (pT) single nonphotonic electrons which have been measured in the RHIC experiments come dominantly from heavy meson decay. The ratio of their pT spectra in pp and AA collisions [RAA(pT)] reveals the energy loss of heavy quarks in the environment created by AA collisions. Using a fixed coupling constant and the Debye mass (mD[approximate]gT) as the infrared regulator, perturbative QCD (pQCD) calculations are not able to reproduce the data, neither the energy loss nor the azimuthal (v2) distribution. Employing a running coupling constant and replacing the Debye mass by a more realistic hard thermal loop (HTL) calculation, we find a substantial increase in the collisional energy loss, which brings the v2(pT) distribution as well as RAA(pT) to values close to the experimental ones without excluding a contribution from radiative energy loss.