Another thing that I've noticed this morning when debugging this further... Scrolling with the mouse wheel makes the pointer disappear. Moving the cursor to just beyond the window, makes it visible again. Then when moving back over the gvim window it is visible.
Its almost as if some mouse function and/or gvim action cause the cursor to be placed behind the gvim window.
Another thing that I've noticed this morning when debugging this further... Scrolling with the mouse wheel makes the pointer disappear. Moving the cursor to just beyond the window, makes it visible again. Then when moving back over the gvim window it is visible.
Its almost as if some mouse function and/or gvim action cause the cursor to be placed behind the gvim window.