Aha -- that worked perfectly. Thank you.
Now that you've pointed out that it had to do with the argument to that function, I realize I should have searched for a WP function reference page. I just found one in the Codex and I could have answered my own question if I had looked at <http://codex.wordpress.org/Function_Reference/is_page>!
BTW, It would be great if you were able to correct the unbalanced parentheses in the if clause in the code in the opening post to this thread, so others don't run into the same problem I did as a result of copying what alx43 typed and pasting it directly into functions.php without checking that the parentheses are balanced. Don't know whether it's possible for you to edit posts from that long ago, but I thought I'd mention it in the hope of saving you and others a few minutes next time someone like me finds this thread.
Thanks again for your help.