In this paper, the boundedness of all solutions of the nonlinear differential equation (phi(p)(x'))' + alphaphi(p)(x(+)) - betaphi(p)(x(-)) + f(x) = e(t) is studied, where phi(p)(u) = \u\(p-2) u, p greater than or equal to 2, alpha, beta are positive constants such that alpha(-1/p) + beta(-1/p) = 2w(-1) with w is an element of R+\Q, f is a bounded C-5 function, e(t) is an element of C-6 is 2pi(p)-periodic, x(+) = max{x, 0}, x(-) = max{-x, 0}. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.