CopyImage problem

Firstly, I know what people like to say about using CopyImage and ResizeImage on the fly instead of preprocessing it all and sticking the results into an array, but this particular re-size might occur once in any 5 minute window of play, could re-size the image to any one of about 200 different sizes and the game runs at about 3% to 4% CPU usage on my system... so I don't want to hear anything about that. Not today. :p

However, I wondered if anyone could shed some light on this strange problem I have so I can get rid of my dubious work-around. Take a look at the following code. The important function it the one called ResizeBat, which (ignoring the first two lines) simply copies a base image over an existing one and then re-sizes it. You can see I've commented out the normal Blitz command CopyImage and added a call to my own function: myCopyImage (listed below).

Function ResizeBat(num, ammount#)
	batScale(num) = ammount#
	If batScale(num) <=0 Then batScale(num) = 0.1

;	bat(num) = CopyImage (bat(0))
	myCopyImage(bat(0), bat(num))

	ResizeImage bat(num), 128 * batScale(num), 20
End Function


Function myCopyImage(source, dest)
	ResizeImage dest, ImageWidth(source), ImageHeight(source)
	oldbuffer = GraphicsBuffer()
	SetBuffer ImageBuffer(dest)
	DrawBlock source, 0, 0
	SetBuffer oldbuffer
End Function

If I use neither of the copy functions, the re-size works as expected.
If I use the Blitz copy function, neither the copy nor the re-size takes place.
If I use my copy function both the copy and the re-size work fine.
If I use both copy functions (pointless, I know, but I was just testing stuff out by this time) no copying or resizing takes place.


Bizarre!
Any ideas?