First off: I'm on a mac. This just happened: I wanted to collapse the sidebar and reopen it, and saw that View > Hide Side bar had two shortcuts: CMD+B and CMD+K. No idea where the 'K' came from (I did recently install a few packages, among others the Soda theme, Enhanced Sidebar, Bracket Highlighter), so I removed it from the default key bindings file. Using CMD+B didn't close the side bar however. I searched for more 'CMD+K' shortcuts in the default key bindings and found a whole lot. I removed them, but nothing changed, it even got worse: all my shortcuts have now completely gone haywire. CMD+A (Select all) does nothing, CMD+W (Close window) acts as a sort of backspace. Some shortcuts still work, such as increase/decrease indent.
Obviously the best fix is to replace the default key bindings, which I guess I did by reinstalling Sublime Text 2. Nothing changed. The shortcuts in the default key bindings look perfectly OK and the shortcuts displayed in various menus are OK. They just don't work, or do something they're not supposed to. I'm hesitant to remove the complete Application Support/Sublime Text 2 folder.
And no, I don't accidentally have DVORAK or a French keyboard configured
Thanks for your help!