What is it and how can I fix it? (STALKER: Clear Sky)

1) Googled the fsgame.ltx file, download and try to replace it in the game folder.
2) If it doesn't help, copy the saves somewhere and reinstall the game

Valyukh000
was from stalker lost alpha reinstall the file is missing

Most likely the working folder is incorrectly specified in the shortcut

How do you run it, from a shortcut or directly from the executable? If from a shortcut, then in its properties check that the working folder (path) is without the bin folder, that is, for example: C: Program Files stalker - true; C: Program Files stalker bin - it is incorrect, if it does not help, check the presence of this fsgame.ltx file in the game folder (not in subfolders).

Antisocial
and your method is also correct, but at first I didn’t read what and how, and then I understood everything)))