toying with arrays - help pls

Hello Blitzers,

i need a little help with the following piece of code.

I am trying to load an image, slice it into 32^2 tiles, store these in an array and then draw the array.
This works on one computer but on another i get a

Unhandled Exception:Attempt to access field or method of Null object

SuperStrict
Global iwidth%,iheight%
Global twidth%=32,theight%=32
Global tilesx%,tilesy%
Global imagemap:TImage[tilesx,tilesy]

'GFX SETUP

SetGraphicsDriver GLMax2DDriver()
'SetGraphicsDriver GLGraphicsDriver()
Graphics 1024,768,32,60

Function iLoad(image_path:String)
	Local image:TImage = LoadImage(image_path)
	iwidth = ImageWidth(image)
	iheight = ImageHeight(image)
	tilesx%=iwidth/twidth
	tilesy%=iheight/theight
	imagemap = New TImage[tilesx,tilesy]
	DebugLog "Variables Set."
End Function

Function iTile(image_path:String)
	Local animimage:TImage = LoadAnimImage(image_path , twidth , theight , 0 , tilesx*tilesy)
	Local counti%=0
	For Local i% = 0 Until tilesy
		For Local j% = 0 Until tilesx
			imagemap[j,i] = LoadImage(animimage.pixmaps[counti])
			counti:+1
		Next
	Next
	DebugLog "Added "+ counti +" images."
End Function

Function Drawtiles()
	'DebugStop()
	For Local i% = 0 Until tilesx
		For Local j% = 0 Until tilesy
			DrawImage (imagemap[i,j],i*twidth,j*theight)
		Next
	Next
	DebugLog "Tiles Drawn"
End Function

iLoad ("tilerender_test1.bmp")
iTile ("tilerender_test1.bmp")
Drawtiles()
'For Local i% = 0 Until tilesx
'	DrawImage (imagemap[i,3],i*32,0)
'Next

Flip
WaitKey

EndGraphics

I put a debugstop in the Drawtiles Function as this seems to be the culprit.

I just don't understand why this works on some computers but not on others..