  We consider twisted equivariant K--theory for actions of a compact Lie group
$G$ on a space $X$ where all the isotropy subgroups are connected and of
maximal rank. We show that the associated rational spectral sequence \`a la
Segal has a simple $E_2$--term expressible as invariants under the Weyl group
of $G$. Namely, if $T$ is a maximal torus of $G$, they are invariants of the
$\pi_1(X^T)$-equivariant Bredon cohomology of the universal cover of $X^T$ with
suitable coefficients. In the case of the inertia stack $\Lambda Y$ this term
can be expressed using the cohomology of $Y^T$ and algebraic invariants
associated to the Lie group and the twisting. A number of calculations are
provided. In particular, we recover the rational Verlinde algebra when
$Y=\{*\}$.
