At 04:50 27.05.06, Micha Hofri wrote: > inserting \protect in front of the \mathbb in the index entry >solved a long-standing problem --- thanks. But why does it have this >effect? ... well, may depend on where \mathbb is from, maybe that \mathbb is fragile and the preceding \protect delays expansion of \mathbb until typesetting mode. Cheers -- Uwe.