Does "categorymembers" work different from the others? When I try http://en.wikipedia.org/w/api.php?format=xmlfm&action=query&list=emb... it returns exactly the same results as http://en.wikipedia.org/w/api.php?format=xmlfm&action=query&list=emb...
"categorymembers" doesn't seem to be the same - http://en.wikipedia.org/w/api.php?format=xmlfm&action=query&list=cat... returns nothing, while http://en.wikipedia.org/w/api.php?format=xmlfm&action=query&list=cat... returns the list of articles.
--SatyrTN