Yes, this is also an issue we are aware of (I should put it on the list of known issues). You can also bind keys like T and then no longer text chat. The fix is to go to UDKGame/Config and delete UDKInput.ini to get the defaults back (or you could try and load an input preset from the menu as well, though not sure this fixes it).
As for binding keys outside the menus: there are console commands for this that will allow you to bind your own keys/buttons to weapon selection (or any other function). Type any of the following commands in the console (accessed in game by pressing ~ or Ö):
This will clear a binding from a key (useful to clear a binding you can't see on the menu)
Example: "UnbindKeyAxis T" clears anything bound to the T key and makes it non-functional.
SetKeyBindByCommand <key/button> <function> <input type>
This manually binds the key or button you specify to the function you specify. The input type must be 0 for keyboard, 1 for mouse and 2 for joystick.
Example: "SetKeyBindByCommand T GBA_Talk 0" binds the text chat function to T.
Example: "SetKeyBindByCommand MiddleMouseButton GBA_SwitchWeapon3 1" binds the dispersion gun switch to the middle mouse button.
Example: "SetKeyBindByCommand XboxTypeS_B GBA_TeamTalk 2" binds the team text chat to the B button on your controller/joystick.
For a complete list of the key, mouse button and XBox button names to use, see this article
The list of functions you could bind this way are:
-- shows the in-game menu
-- switches to a weapon directly
-- text chat
-- team text chat
-- voice chat
All other functions can be bound through the menus.