Re: C-x keystroke changed at runtime

[Eli Zaretskii]

> From: Michele Bert <micbert75@gmail.com>
> Date: Tue, 20 Sep 2016 10:42:42 +0200
> 
> After more than 1 week that it has been running (continuosly: I use to
> leave it always open, even during the night, opening and closing
> buffers, creating new frames, even with aid of emacsclient), suddenly
> (few minutes ago) the C-x keystroke has changed behavior: whenever
> there is an active region, it kills the selected text (just like C-w),
> while if there isn't any region, it acts as a prefix for the usual
> keystrokes (I can visit a file with C-x, C-f, or save it with C-x,
> C-s, or change buffer with C-x, b, for example). But with an active
> region it kills it instantly.
> 
> I am going to restart the program, but before doing it, I would be
> very curious to understand what is happening, so if anyone has a
> suggestion about some tests or checks I can do, I would appreciate.

Crystal ball says you've turned on CUA mode.  What do you see in the
mode line, where minor modes are shown?  What does "C-h m" tell you
about the active modes?