This happens on Windows 7 if you have more than one input language. Ctrl-Shift-0, Ctrl-Shift-1, ... are designed to quickly switch the input language. This seems to be impossible, because Windows intercepts certain key combinations (for example, Win-E, Win-D, etc.) and does not pass it to the application. Perhaps worse, the Intel GMA driver does not allow the use of Ctrl-Alt-Up / Down in Win XP.
Just use a different shortcut in Emacs (or you can try reassigning keys with tools like Sharpkeys).
EvgeniySharapov
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