Stephen, if his keyboard was not working, his statement in the original post, would not make any sense.
The Ctrl + C error isn't in e-Sword. If a thorough test is done using that keystroke right across the board in other applications which uses text, then that error should come up right across the board of all his applications (programs). Moreover, if the error was in John's copy of e-Sword 11.10, then that error would appear in all copies of that version of e-Sword. But because that is not happening, and it's only localized to his machine.
Not only that, but also if he tested the other methods of copying using the Copy menu item in the popup context menu, and Copy button and doesn't get that error using them, then the issue has to be related to hardware. That said, if he does get that error using the other methods of Copy, and that same error appears in his other applications, such as MS Word or whatever he uses, then he has a hardware issue of which the CPU or something else is not registering the command. Even a simple loose connection of the keyboard, I've learned, can cause that error.
It would be interesting to know when that error began to occur because John would have used that keystroke many times before it occurred without any problems. So, in order to know how, when and where that began to occur a great deal of more information is needed.