Have a quick look at the descr_strat file you are using. The early versions had the win_conditions section I've marked in bold, near the top:
...thrace
numidia
slave
end


start_date -270 summer
end_date 14 summer


win_conditions
land_owner 20 100
land_owner 20 100
land_owner 20 100
land_owner 20 100
land_owner 20 100
land_owner 20 100
land_owner 20 100
land_owner 20 100
end_win_conditions

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; >>>> start of landmarks section <<<<

landmark pyramids_and_sphinx 181, 12....
1.5 shouldn't have that and that will generate the error you are getting as 1.5 no longer recognises it.
If you have that try deleting that whole section.

If I understood you right and you patched over a modded version you may have other problems as well though