  We study, at T=0, the anomalies in the magnetization curve of the S=1 two-leg
ladder with frustrated interactions. We focus mainly on the existence of the
$M=\Ms/2$ plateau, where $\Ms$ is the saturation magnetization. We use
analytical methods (degenerate perturbation theory and non-Abelian
bosonization) as well as numerical methods (level spectroscopy and density
matrix renormalization group), which lead to the consistent conclusion with
each other. We also touch on the $M=\Ms/4$ and $M=(3/4)\Ms$ plateaux and cusps.
