  We prove that for q\in\C* not a nontrivial root of unity the cohomology group
defined by invariant 2-cocycles in a completion of Uq(g) is isomorphic to
H^2(P/Q;\T), where P and Q are the weight and root lattices of g. This implies
that the group of autoequivalences of the tensor category of Uq(g)-modules is
the semidirect product of H^2(P/Q;\T) and the automorphism group of the based
root datum of g. For q=1 we also obtain similar results for all compact
connected separable groups.
