A model of weakly magnetized, isothermal accretion disk with the diffusion-type viscosity is investigated in this paper. The pulsational instability of the disks, arising from nonaxisymmetric perturbations (including radial, azimuthal and vertical perturbations) is discussed on the ground of the authors previous work. It is shown that the radial perturbation is the most important and essential one. There are no pulsational instabilities arising from either azimuthal or vertical perturbations in the absence of the radial perturbation. In contrast, in the presence of the radial perturbation, the...
