Obtaizen and for people like us that can't load Tranzit, you just have to comment/delete this line in the souce code :
if( getdvar( "mapname" ) == "zm_transit" )
level._effect[ "jetgun_smoke_cloud" ] = loadfx( "weapon\thunder_gun\fx_thundergun_smoke_cloud" );
I think the Thundergun is from Black OPS 1 so is this piece of code.
Now Transit work peacefully!