I press "1" key, switches windows?

This is such a ridiculous question that I'm sure has been answered innumerable times, but I cannot figure out how to turn this off.
When I press the 1 key on my keyboard, I can't cast spells, but instead my ISBoxer switches windows. Help, please!

[lax]

You're only pressing "1"? Not holding, say, Ctrl and Alt (or AltGr, which is the same thing as Ctrl+Alt)?

Because there's a default hotkey Ctrl+Alt+1 to bring up window 1, and Ctrl+Alt+2 to bring up window 2, and so on. To change this, select your Character Set in the top left pane, then in the bottom left pane select each Slot number (e.g. 1, 2); the Hotkey option should then be at the top of the bottom right pane.