Emacs on Putty suddenly stopped accepting ctrl-space?

Question

Weirdly, ctrl-space to start a mark works on the command line in putty and on X on the machine, just not in putty. What configuration did I break?

Answer 1

take a look at http://stackoverflow.com/questions/179119/how-to-prevent-windows-xp-from-stealing-my-input-ctrl-space-which-is-meant-for-em

Answer 2

That other question doesn't apply, because the ctrl-space is sent to the command line in putty, just not to emacs.