Based on a simplest model (the Shenly column), we consider some principle peculiarities of the phenomenon of stability loss of deformable solid bodies in the case when their constitutive equations include the derivatives of deformations with respect to time. We analyze the cases of steady state creep and straight thermoelastic phase transformation, which are typical for the alloys with shape memory. We discover that the classical approach to estimation of the stability in linear statement brings us to incorrect results and propose an algorithm for this problem solution. We also discover that accounting for the coupling of the problem of stability under straight thermoelastic transformation decreases the critical force in two times.