I'm using LR4 on 2 screens; with the grid module on one screen, develop module on the other. When I select a photo from the grid on screen 1, then move to the develop module on screen 2, as the pointer moves across the grid module the last photo that is touched from the various thumbnails on the "grid" is the picture that gets displayed as the develop module "navigator" picture in the upper left corner. The picture I selected remains in the main screen of the develop module, but the upper navigator picture is whatever the mouse pointer touched last on the grid screen. Zooming and scrolling in the "navigator" window will move the develop module main window to the equivalent point location though the pictures are different.
Thanks, hopefully I have described the bug sufficiently.