The anomalous dispersion found by inelastic neutron scattering in one of the vibron bands in solid tetracyanoethene appears to be due to the electrostatic interactions that couple the infrared-active intramolecular vibrations via the transition dipole resonance mechanism. This is demonstrated by way of both numerical lattice dynamics calculations and a simple mathematical analysis, which relates the Fourier components of the dispersion curves in specific directions of the wavevector k to two-dimensional lattice sums over the dipole-dipole interactions between layers perpendicular to k. Only for specific orientations of the molecular transition dipole moments in a solid and for specific directions of k will this lead to a dispersion curve of irregular shape.