Sudoku Puzzle Solver II

I've rewritten my Sudoku solver -- it solves many more puzzles than before, including, it seems, the Evil ones at http://www.websudoku.com/.

I thought I had licked the Sudoku habit. But then Cédric Beust mentioned his addiction, and now here I am back at it. My wife's addicted now, too.

I'm pleased that it solves many more puzzles, but I'm clear that a trigger-based rule system would be much more elegant. Plus a more general solution, one that solves puzzles of arbitrary size, would satisfy my soul. There are also those puzzles with multiple solutions; this might very well merely get stuck. Of course, I may never pick it up again. and may have to be satisfied despite remaining unable to be as organized as the computer in solving these impish knots.

See the revised solution here.