I added a new slide, clicked on the "Click to add title" text, and found that
when I typed, nothing came out.  Apparently there was no blinking cursor in the
title text box.  When I clicked in the box again, then the cursor appeared, and
I was able to type.  However, if I delete all text, click out, and click again
on the "Click to add title", the problem recurred.

I saved the file, but when I re-opened it, and clicked on this title box again,
the cursor appeared correctly.