It's likely that Wilbur is still doing something. To get OpenMP things to work properly I had to sacrifice the user update dialogs for some operations. If the Program Manager is showing 100% CPU then Wilbur is probably doing something useful like calculating flows ( an O(n*n*n) so it can get extremely slow - hours slow - on larger surfaces ).

As an aside, I haven't used the Erosion Cycle thing in several years and don't remember its precise algorithm.