Don't know exactly how, but it turns out this problem began after I tightened-up some security features within my PC and my anti-virus program.
Full-functionality of RP is back after relaxing a few settings back, but don't know which particular setting(s) caused this.
So, I've now learned something new about paying more attention to
inter-relationships among different programs possibly affecting others when settings are changed. And now after making a change to one program's settings, I start each/all programs to check if changed.
I was pleased when the last RealPlayer update allowed a new recording to HD of streaming flv files feature, new to me. Recently the dropdown with that option and the others is gone.
I want to know if this change on my PC is because something changed in the public domain, RealPlayer, YouTube, etc change, or I have missing or corrupted files in PC.