Not sure, but it's possible there was a copy
running under the same user. Thanks for that hint.
I have just opened a fresh gthumb without problems
so that may well have been the trouble.
I am running SL 7 and a gthumb from nux.

Malcolm MacCallum
________________________________________
From: [log in to unmask] <[log in to unmask]> on behalf of Mark Stodola <[log in to unmask]>
Sent: 13 February 2017 22:04
To: [log in to unmask]
Subject: Re: gthumb now giving an error

On 02/13/2017 03:40 PM, MAH Maccallum wrote:
> I have been using gthumb happily for a while. It has
> suddenly started to evoke the error message;
>
> GDBus.Error:org.freedesktop.DBus.Error.NotSupported: Application does not handle command line arguments
>
> This happens even when no argument is given on the command line.
> Does anyone know why this has started to happen? (Since it did not happen
> before it cannot be an error in the program itself surely...?)
>
> Malcolm MacCallum
>

Do you already have a copy of gthumb running under the same user?  I
think this was a bug in F20 and fixed in F21 a few years ago.  Not sure
what versions they are/were compared to whatever SL you are running (you
didn't specify which major release you are on).