We prove a conjecture in [L11] stating that certain polynomials P-Y(sigma),(w)(q) introduced in [LV11] for twisted involutions in an affine Weyl group give ( -q)-analogues of weight multiplicities of the Langlands dual group G. We also prove that the signature of a naturally defined hermitian form on each irreducible representation of e can be expressed in terms of these polynomials P-Y(sigma),(w)(q).National Science Foundation (U.S.) (Grant DMS-0758262)National Science Foundation (U.S.) (Grant DMS-0969470)