The viscoelasticity of aqueous micellar solutions of two oxyethylene/oxybutylene block copolymers (E92B18 and B20E510) has been investigated using a torsional resonator operated at 26 kHz. For both systems considered, values of the dynamic viscosity (eta'(infinity)) point to partial draining of the micellar corona induced by the high-frequency oscillatory field. At low effective volume fractions, values of the elastic modulus (G'(infinity)) indicate that the repulsive interactions between micelles can be modeled by a power law function u(r) proportional to 1/r(v) with exponents close to 13 and 6 for copolymers E92B18 and B20E510 respectively. At a critical copolymer concentration (c*) plots of log(G'(infinity)) against log(c) deviate from the straight lines established at low concentrations, implying that the systems undergo ergodic/nonergodic transitions.