In regards to the unknown cause for the remaining question as to what determines this error, I noticed in Far Cry ran on Windows 7 x64 some graphical glitches regarding increasing drawing distance(it seems that they were always present even during the XP days) and also some graphical glitches when you zoom in and then out in the distance or turn around while first looking at the ocean, then for a few seconds at the land and then back to the ocean. The fort level is great for testing that.
I don't quite remember what happens in the first case, either the sky disappears or becomes black, and with the ocean glitch something similar but related to the ocean.
If you turn off terrain occlusion culling or parts of it(which are directly correlated with the clip planes method) by way of console variables it introduces again graphical glitches.
I once again uninstalled Far Cry and I don't quite remember how the graphical glitches manifested, either sky, land, ocean disappearance/black areas or missing textures.
Even though Far Cry uses plane clipping I could only find one console variable regarding frustum which is p_lightfrustum. I kept it at default. I wonder if it solves some of the problems by increasing it.
I don't have the possibility of testing the game on a XP machine but if you can and you don't encounter any errors on increasing drawing distance and turning off occlusion culling then you might be able to isolate the issue.
There is another glitch happening when e_particles_receive_shadows(a new variable introduced in a later patch, present in 1.32 though) is turned on. It is a graphical glitch involving the ocean. Again the fort level is recommended for testing it.
Anyway, thanks a lot again for fixing it on Windows 7 since with the current trend of disregarding compatibility with every major Windows 10 update coupled by also forcing the updates, things don't look very bright for older applications.