We study the effect of a right-handed coupling of quarks to the
W-boson on the measurements of |V_{ub}| and |V_{cb }|. It is shown that
such a coupling can remove the discrepancies between the
determinations of |V_{ub}| from B\to \pi \ell \nu, B^+\to \tau^+
\nu and B\to X_u \ell \nu. Further the measurements of |V_{cb}|
from B\to D^* \ell \nu, B\to D \ell \nu and inclusive B\to X_c
\ell\nu decays can be brought into better agreement. We demonstrate
that a right-handed coupling can be generated within the MSSM by a
finite gluino-squark loop. The effect involves the parameters
\delta^{u RL}_{23} and \delta^{u RL}_{13} of the squark mass
matrices, which are poorly constrained from other processes. On the
other hand, all gluino-squark corrections to the regular left-handed
coupling of the W-boson are found to be too small to be relevant.