After fitting the first shell of some standard data to determine the correct value of S02, I proceeded to start defining the next feff file and the following errors appeared (and artemis stopped responding) Use of uninitialized value in concatenation (.) at /usr/local/bin/artemis line 3684. Tk::Error: Can't call method "make" on unblessed reference at /usr/local/bin/artemis line 2171. Tk::Widget::Callback at /Library/Perl/darwin/Tk/Widget.pm line 988 Tk::HList::ButtonRelease1 at /Library/Perl/darwin/Tk/HList.pm line 298 Tk::HList::ButtonRelease_1 at /Library/Perl/darwin/Tk/HList.pm line 94 (command bound to event) Tk::Error: Can't call method "make" on unblessed reference at /usr/local/bin/artemis line 2171. Tk::Widget::Callback at /Library/Perl/darwin/Tk/Widget.pm line 988 Tk::HList::Button1 at /Library/Perl/darwin/Tk/HList.pm line 181 (command bound to event) Tk::Error: Can't call method "make" on unblessed reference at /usr/local/bin/artemis line 2171 I also noticed that the feff paths were ordered in something like ascii collating sequence as opposed to numerical ranking, e.g. 0001,0002,0011. I enclosed a small snapshot of the window. Any idea why this might be happening?