Just a guess. When drawing the background, try using DrawBlock instead of DrawImage. Either that or use MaskImage to change the mask. Since the mask is set to 0, it may just not be re-drawing the black parts of the picture each frame, and so it leaves bits of the cursor.
Looks like you've got an interesting idea for a game there - fun! I'd like to give it a try when you get it playable.
Looks like you've got an interesting idea for a game there - fun! I'd like to give it a try when you get it playable.