Recent data on single-electron elliptic flow (v2) in Au-Au collisions at RHIC have given intriguing indication for a collective behavior of charmed hadrons. Motivated by recent lattice-QCD calculations, we investigate [1] consequences of resonance formation in a Quark-Gluon Plasma (QGP) by constructing an effective model for low-lying D-meson states compatible with both chiral and heavy-quark symmetry. Calculating pertinent drag and diffusion coefficients for resonant $c+\bar q\to D$ interactions, we find a reduction of c-quark thermalization times by a factor of 3 compared to perturbative QCD cross sections. Pertinent electron pt-spectra and v2 are computed using a Fokker-Planck equation within an expanding QGP fireball, including coalescence at Tc. A similar analysis for bottom quarks reveals much longer thermalization times, with important consequences for (suppression of) bottomonium vs. (regeneration of) charmonium production. [1] H.van Hees + R.Rapp, PRC71 (2005) 034907