It's with any application. Examples include Pages, Safari, Text Editor, Textmate, really everything.
Following Carolyn's advice I tried prepending the 'fn' modifier with no results. But it did get me poking around and I found that shift-command-s DOES work.
But I don't EVER recall having to do this in the past. And I don't have to use the shift key with any other common command shortcut; i.e. comand-x, command-v, command-p, command-q, command-w . . . you get the idea.
Thanks everybody for your help so far. I could probably just use the shift-command-s, but it would bother me that something is dorked up somewhere and I'm wondering what the next thing will be.