animation on top of screen invisible

Hi folks!

I'm writing a pacman-like game in BP7 and till now everything went good.
But now I have the following problem : there is an area on the top of the
screen (the first one or two inches) where all the static pics (like the
maze ...) are shown, but not the moving ghosts and pacman.
I'll explain it a little bit more :

I'm using a graphical library (vesatp11, found on x2ftp and also available
on garbo). My program runs in 640x480x256. This is what happens :
First of all I draw a background on the screen (the pacman-maze).
Then I back up the background on the places where the ghosts and the
pacman are going to appear. I use the getimage pascal commando for that.
Then put the ghosts and the pacman on the screen using the putimage
commando. I put the background backups on the screen again and move
(this is add a value to the x and y positions of the ghosts and the
pacman) the pictures. Then I draw them again, etc.
This all works very good and give smooth animation without flikkering.
When I put only one ghost and the pacman on the screen : no problem.
With two ghosts and the pacman, also no problem. But than, when I draw
three ghosts and the pacman, the troubles starts : there is a region (on
top
of the screen, the first half inch of the screen) where the maze is shown,
but not the pacman and the ghosts (they disappear there). When I try
four ghosts and the packman, the region is bigger (first inch of the
screen).
I saw that the more ghosts I draw on the screen, the bigger the region
on top of the screen is.
In the region where the pacman and the ghosts disappear, I can see the
pacman move because he is eating his "candy's" there. The candy's
disappear when you move the pacman over them, but you don't see the
pacman.
I really have no idea what is wrong. Is there someone out there who
can give me a clue for this?

I'll be very thankfull for all your help.

Peter.
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