Video memory not restored

;Positioning my entity results in video memory not being ;restored? Here is the section of code. The comments
;explain the situation,I'm very confused ;(

;Is this a bug with blitz3d or my set up, or just too many ;hours without a break?
;XP,768 RAM,althon 1.8 gig,Radeon 9600

Const GFX_WIDTH = 800
Const GFX_HEIGHT = 600
Const GFX_XCENTER = GFX_WIDTH/2
Const GFX_YCENTER = GFX_HEIGHT/2

Graphics3D GFX_WIDTH,GFX_HEIGHT,16,2
SetBuffer BackBuffer()
SeedRnd (MilliSecs())
HidePointer()

Global INITIAL_MEM = AvailVidMem()

Global CAMERA = CreateCamera()
; store texture in Vram
Global LOGO = CreateTexture(512,512,1+256)

Global INFOPLANE = CreateSprite()
ScaleSprite INFOPLANE,2,1.5
EntityFX INFOPLANE,1+8+16
EntityTextureINFOPLANE,LOGO

; REM out the line below and videomem is restored to the ;initial value as required
PositionEntity INFOPLANE,0,0,2

;However leave it in and the video memory does not get ;restored, or so it would appear.

;....but leave in positionentity() and REM out renderworld ;and memory is restored?

RenderWorld

Text 0,12,"Initial Video mem : "+ INITIAL_MEM
Text 0,24,"Current Video mem : "+ AvailVidMem()

;MouseWait

; FreeTexture LOGO ;\
; FreeEntity INFOPLANE ; same result as clear world
; FreeEntity CAMERA ;/

ClearWorld

Text 0,36,"clear world Video mem : "+ AvailVidMem()
Flip

MouseWait

End

Add RenderWorld after ClearWorld.

that gives me back most of the memory but I'm still 40K down.

Don't know why renderworld would free memory anyway?
does it clear a memory buffer on the video card?

I tried updateworld and that doesn't work either...

probably it's a memory segmentation problem.

on my comp, renderworld solves it...

EndGraphics