The program 'gksu' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadWindow (invalid Window parameter)'.
(Details: serial 841 error_code 3 request_code 2 minor_code 0)
(Note to programmers: normally, X errors are reported asynchronously;
that is, you will receive the error a while after causing it.
To debug your program, run it with the --sync command line
option to change this behavior. You can then get a meaningful
backtrace from your debugger if you break on the gdk_x_error() function.)
Timeline is critical here, the error is telling that the program gksu tried to access a "window" who's ID is actually unknown,
in turn this could be the result of a delayed mapping of the window, which is something that depend from the window manager.http://www.rahul.net/kenton/40errs.html#Error3
Because of multiple DE install, I suspect JohnW is using a different window manager or a different window manager set up, that trigger the error, while the error itself probably is in gksu. Not easy to track it down.JohnW
Just for confirmation you could try something like that, from a non root user account:
gksu -l synaptic
this should trigger the same error as shown from lomanager...