Perhaps one of the reasons the application wasn't working 100% was because I had two browsers, Thunderbird and iTunes open (but not playing) while poor SuperDuper! was trying to copy things?
I guess I have those things on so much (iTunes not as much but still) that they've become kind of a constant and I don't even notice them just sitting there in the background, ready to leap up back at my beck and call with a click of a button.
Once I closed them down and ran SuperDuper!, all was well - for the moment. But since I so rarely have them all closed at once, I'm wondering if it may be that iTunes especially is loathed by SD or by some weird happenstance, the last time I ran SD all the applications were closed.
Maybe in light of the panic I was feeling when my hard drive started acting weird, applications that were rock stable started to crash and I was looking at SD to save my sanity (and files).
It really did both, btw
I'll have to try to remember to shut down everthing before automatically running SD... .