[AdamB]

yes i also had ctd when i brought it new. to prevent this go into steam and verify the games cache and if all the files have not been downloaded the next time you log onto steam it should just download the game again or update the game or if installing from disk try re-installing. i am sure that the black lines are caused by a bug. (i have the same problem in the tiger moth). the 'high' setting is not the best and will downgrade the texture slightly whereas the original setting keeps the maximun textures at the cost of 2-3 fps over water and 5-9 over land. looking at your sys. spec. i dont think you couldnt run the grass option at that resolution as CPU wont be able to load it fast enough.

my advice to you is to run the game at Resolution - 1240x720
Buildings - very low/low
Model Detail - high
Forest - low/medium
Land detail - medium/high
Land shading - high
Grass - on
Shadows - off
SSAO - on
Texture quality - high/original
Buildings amount - very low/low