Without information about the version you use and your system specs it's only fortune telling but Libertalis isn't just imporving Arx Fatalis but also raising the requirements(Dx9 instead of Dx7 for example) and upgrading/removing API's that where rated as outdated or unnecessary.
Modern graphic card can directly communicate complex orders with the programm(game) older ones often couldn't.
Or more simple, if you have a older graphiccard it might not be able to understand the orders Arx Libertalis is sending because the API's they need to communicate are not supported by Libertalis any more.
Well i am trying to run it in QHD resolution in Windows 10 running a GTX 1050 Ti graphic card. 1920x1440 works fine but not 2560x1440, then it crasches.