GTK 2.6.9
GIMP 2.2.8

To reproduce:
1.  Create a new image, a fairly large one that is very wide and/or very tall
(like 1024x120).  Image content or usage of layers don't matter.
2.  Zoom in and/or shrink the image window just enough so you have a scroll bar
(whether horizontal and/or vertical, it doesn't matter) where some scrolling is
needed.
3.  Choose any of the selection tools (rectangle and ellipse is what I used) in
either replace or add mode.
4.  Make a selection somewhere, small enough so that, when you scroll, it'll be
off the screen.
5.  Scroll somewhere so that the selection you just made is not on the screen
any more, but still present.
6.  Make another selection (in replace or add mode).  You can make the selection
with the previous selection in the view and go off the edge of the image to
scroll to also get the same effect.
7.  This time, you won't see anything appear at all even after several seconds.
8.  Scroll a little in any direction and you'll then see the selection you just
made in step 6, even a very tiny amount of scrolling is all you need.
9.  Repeat steps 4 through 6 only click on a different window and return to the
image window instead of scrolling.  It appears this way as well.

Whether you have multiple selections (selected areas) or not, or even have
another image window open with selections visible in it, when you make a
selection, as long as the selection you make is in an area where no selection is
visible in the current image window, the selection won't appear until you either
scroll or return to the window where the selection didn't appear.

Running Windows 98 SE on a Pentium 4 processor (3.0 GHz) with 512 megabytes of
DDR RAM and a Radeon 9600 XT video card (running at 1600x1200 resolution at
32-bit color) with DirectX 9.0c.