Alt+something hotkeys cause Windows error chime when playing Windowed mode

Steps to reproduce:

1. Bind Inventory to Alt+C
2. Go to Options and switch into Windowed mode
3. Save changes to Options and close Options
4. Press Alt+C
5. Inventory panel opens correctly, at the same time Windows exclamation chime plays

I'm assuming the game is passing the hotkey along to Windows.

This makes the Alt modifier unusable for hotkeys in windowed mode.