issue with emacs-25.1-1

[Wendell MacKenzie]

Hi:

   Long time emacs user...since the 80's.  Since installing emacs-25.1 on
my redhat enterprise server, gdb (7.12) is not working as usual.  When I
have the source file open in one window and a gdb window open in another
window with a program loaded
in the source window I can usually using the sequence: CTRL-x space to
toggle
a breakpoint on that line of code the cursor is on.  This is not working
anymore.

   Any idea what might have changed that would affect this behavior?

thx
W. MacKenzie