ERROR: Could not find zone

Hello

I was attempting to install a custom zombie mod, then i got this error.

ERROR: Could not find zone 'C:\Program Files\Activision\Call of Duty - World at War\zone\(null)\code_post_gfx.ff'

I was booted back to my desktop and havent been able to play since. I didnt delete anything, change anything, or move anything. Could you please help.

Also before I get this error i get a message saying "WIN_IMPROPER_QUIT_BODY" and my options are YES  NO   CANCEL and no matter which i choose (except cancel) i get the above noted error