Well, you're right, Tec and Beeb, the same 9-letter word did come up twice, but it wasn't meant to happen. I discovered it later and thought I'd got away with it, but I obviously can't put anything over on you lot! (I'd actually played both puzzles myself without noticing anything was wrong - I probably just assumed I must have had the word recently in a random puzzle.)
For the trivia buffs, the word was flabbiest (appropriately enough perhaps - my programming skills had seemingly been at their flabbiest), and it came up in the Challenge puzzles for 27 and 31 December 2006. The first time the mandatory letter was S and there were 109 words possible; four days later the mandatory letter was A and 134 words could be made.
The way things are meant to work is that no nine-letter word that has been used in a daily puzzle can be used again, even with a different compulsory letter. Obviously, that rule will have to be relaxed eventually, but at the moment we still have over three thousand eligible nine-letter words that haven't been used in daily puzzles. (Although most of them have been used in random puzzles.)
