My selection window has suddenly disapeared. The typical selection window
has a bold line around your selection, and is slightly shaded blue... but
mine doesn't show anything at all. I can still select a group of cells, and
copy them, but there is no way for me to preview what I'm selecting or
copying.

I've gone through all the settings, and I can't see anything that would give
me an option to change this. Any help? Thanks!