Not knowing exactly what a "GPF" is I googled it. For my own sanity, this is what I found:
Short for General Protection Fault, a computer condition that causes a Windows application to crash. The most common cause of a GPF is two applications trying to use the same block of memory, or more specifically, one application trying to use memory assigned to another application.
The following situations can also cause GPFs.
Running an application with insufficient resources
Using improper hardware device drivers
Corrupted or missing Windows files
Applications exchanging data that cannot be read
GPFs are often preceded by an invalid page fault.
So have you checked your system for any/all of the above?
Because I get no graphical window I am not sure how to edit the code, are the source files available to be edited in a program editor
You will not find the source code for Xlobby anywhere except for Steven's hard drive. He has not publicly released it, nor (it seems) he is willing too. Too bad though as there has been some bugs with the latest release, but with him so busy with Xlobby3, these may never be corrected.
When it launches does it read a configuration file on startup?
I'm not totally sure of everything it reads on startup, but it does use the xlobby.xml file to help configure itself. Most of the files it uses to configure itself (outside of the source code) is by .xml file types.
Hope this was helpful.