Beauticat has totally changed their formula. There were always mild variations in the litter. It might be slightly lighter or darker depending on the bag, but never dark, dark, and it always smelled and worked the same. Beauticat has changed its name (I don't know if they were always owned by Sophisticat), and since then, the litter has been less consistent. The last bag we bought was dark and smelled awful. When my cat used it, it turned into a horrible rank dark mush. Even he didn't know what was up. For a cat very tolerant to changes in litter (in fact he took in the idea of wood litter without much of a notice), he was very wary of that bag of Beauticat.
So, we're trying Bio-Catolet Cat Litter. It's good so far, except it really doesn't do a great job in the pee masking smell. I changed the first box of it last night, and it nearly knocked me over. I guess we could go back to non-clumping clay, but it is relatively hard to find. The only non-clumping clay our local Sainsbury's is Basics. I am not all that adverse to trying a cheap litter (our one in the States was v. cheap and worked a treat), but the lugging it and not having it work would be a pita.
I guess I will try our new Morrisons. Gives us an excuse to check it out anyway.