memory access violation

Ok guys, here is my problem!
I'm getting a memory access violation! when i run my program. don't worry about not seeing anything, I know the program is not complete!. Another thing, I program in modules. This makes correcting mistakes a lot easier!!!

There are three files altogether

1. The main file

Include "Collisions.bb"
Include "Setup.bb"
Include "World.bb"
;Include "Player.bb"
;
; ===============================================
;
;   These files are not necessary for this particular game-script but they help out in coding
Include "key function.bb"



;
;        Main Routines
;

SetBuffer BackBuffer()
Setup
landscape("terrain-1.bmp", "water-2_mip.bmp", "sky", "heightmap_256.bmp")
Flip
UpdateWorld
RenderWorld
WaitKey()

2. A sub-program

;  SetUp file

Type MainCamera
		Field entity,camera,target,heading,sky
End Type
Type Player
	Field entity,model
	Field anim_speed#,player_y#,roll#
End Type


Function SetUp()
	Graphics3D 800, 600, 32, 0
	Player1.Player = CreatePlayer(0,10,0)
	Player1Camera.MainCamera = CreateMainCamera(Player1\entity)
End Function

Function CreateMainCamera.MainCamera(entity)
	c.MainCamera=New MainCamera
	c\entity=entity
	c\camera=CreateCamera()
	
	c\target=CreatePivot( entity )
	PositionEntity c\target,0,3,-10
	EntityType c\target,TYPE_TARGET
	
	c\heading=CreatePivot( entity )
	PositionEntity c\heading,0,0,20
	c\sky=CopyEntity( sky )
	Return c
	
End Function
Function UpdateMainCamera ( c.MainCamera)
	If KeyDown(200)
		TranslateEntity c\heading,0,-3,0
	Else If KeyDown(208)
		TranslateEntity c\heading,0,+3,0
	EndIf
	
	dx#=EntityX(c\target,True)-EntityX(c\camera,True)
	dy#=EntityY(c\target,True)-EntityY(c\camera,True)
	dz#=EntityZ(c\target,True)-EntityZ(c\camera,True)
	
	TranslateEntity c\camera,dx*.1,dy*.1,dz*.1
	
	PointEntity c\camera,c\heading
		
	PositionEntity c\target,0,0,0
	ResetEntity c\target
	PositionEntity c\target,0,3,-10

	PositionEntity c\sky,EntityX(c\camera),EntityY(c\camera),EntityZ(c\camera)
	
End Function

Function CreatePlayer.Player(x#, y#, z#)
	
	p.Player=New Player
	p\entity=CreatePivot()
	p\model=CopyEntity( player_model,p\entity )
	p\player_y=y
	PositionEntity p\entity,x,y,z
	EntityType p\entity,TYPE_PLAYER
	EntityRadius p\entity,1.5
	ResetEntity p\entity
	Return p

End Function

3. Another sub-program

Function skybox(file$)
	
	m=CreateMesh()
	;front face
	b=LoadBrush( file$+"_FR.jpg",49 )
	s=CreateSurface( m,b )
	AddVertex s,-1,+1,-1,0,0:AddVertex s,+1,+1,-1,1,0
	AddVertex s,+1,-1,-1,1,1:AddVertex s,-1,-1,-1,0,1
	AddTriangle s,0,1,2:AddTriangle s,0,2,3
	FreeBrush b
	;right face
	b=LoadBrush( file$+"_LF.jpg",49 )
	s=CreateSurface( m,b )
	AddVertex s,+1,+1,-1,0,0:AddVertex s,+1,+1,+1,1,0
	AddVertex s,+1,-1,+1,1,1:AddVertex s,+1,-1,-1,0,1
	AddTriangle s,0,1,2:AddTriangle s,0,2,3
	FreeBrush b
	;back face
	b=LoadBrush( file$+"_BK.jpg",49 )
	s=CreateSurface( m,b )
	AddVertex s,+1,+1,+1,0,0:AddVertex s,-1,+1,+1,1,0
	AddVertex s,-1,-1,+1,1,1:AddVertex s,+1,-1,+1,0,1
	AddTriangle s,0,1,2:AddTriangle s,0,2,3
	FreeBrush b
	;left face
	b=LoadBrush( file$+"_RT.jpg",49 )
	s=CreateSurface( m,b )
	AddVertex s,-1,+1,+1,0,0:AddVertex s,-1,+1,-1,1,0
	AddVertex s,-1,-1,-1,1,1:AddVertex s,-1,-1,+1,0,1
	AddTriangle s,0,1,2:AddTriangle s,0,2,3
	FreeBrush b
	;top face
	b=LoadBrush( file$+"_UP.jpg",49 )
	s=CreateSurface( m,b )
	AddVertex s,-1,+1,+1,0,1:AddVertex s,+1,+1,+1,0,0
	AddVertex s,+1,+1,-1,1,0:AddVertex s,-1,+1,-1,1,1
	AddTriangle s,0,1,2:AddTriangle s,0,2,3
	FreeBrush b
	;bottom face	
	b=LoadBrush( file$+"_DN.jpg",49 )
	s=CreateSurface( m,b )
	AddVertex s,-1,-1,-1,1,0:AddVertex s,+1,-1,-1,1,1
	AddVertex s,+1,-1,+1,0,1:AddVertex s,-1,-1,+1,0,0
	AddTriangle s,0,1,2:AddTriangle s,0,2,3
	FreeBrush b
	ScaleMesh m,100,100,100
	FlipMesh m
	EntityFX m,1

End Function
Function landscape(land$,water$,sky$,heightmap$)
	
	light=CreateLight()
	TurnEntity light,45,45,0
	
	land_tex=LoadTexture( land$,1 )
	ScaleTexture land_tex,10,10

	land=LoadTerrain( heightmap$ )
	EntityTexture land,land_tex
	
	TerrainShading land,True
	PositionEntity land,-1000,-100,-1000
	ScaleEntity land,2000.0/256,100,2000.0/256
	EntityType land,TYPE_TERRAIN
	TerrainDetail land,750,True
	
	For k=1 To n_trees
		Repeat
			tx#=Rnd(-70,70)-150
			tz#=Rnd(-70,70)+400
			ty#=TerrainY( land,tx,0,tz )
		Until ty>water_level
		t=CopyEntity( tree_sprite )
		PositionEntity t,tx,ty,tz
		ScaleSprite t,Rand(2,3),Rand(4,6)
	Next
	
	ground=CreatePlane()
	EntityTexture ground,land_tex
	PositionEntity ground,0,-100,0
	EntityOrder ground,9
	
	water_tex=LoadTexture( water$,3 )
	ScaleTexture water_tex,20,20
	
	water=CreatePlane()
	EntityTexture water,water_tex
	PositionEntity water,0,water_level,0
		
	sky=skybox( sky$ )
	EntityOrder sky,10
	HideEntity sky

End Function