Seems like I just can't get rid of issues in this game... This time with Team Editor.

It says "impossible to find car_collision_mesh.ct in the wad" when opening, then stops working, then writes an error message in what appears to be in spanish language.
Fix?

I use a 1.02 decrypted GP4 on W7, the game works perfectly.

Basic question: is a fresh cars.wad or a modified one? did you check that the file car_collision_mesh.ct exist inside the cars.wad file?