It wasn't quite the "And then my troubles began..." experience like the BIOS reflash in January, but I was very amused by the fact that XSANE both throws a dialog box containing the following words:
You are trying to run Xsane as root! This is DANGEROUS! Please do not file bug reports for anything that happens when running Xsane as root: YOU ARE ON YOUR OWN!and also suggests running as root as a generic troubleshooting option in its documentation. Well, I did, and all went OK. As I said to Soizick: the great thing about using Linux is that you get to feel like a mad scientist.
I recommend and endorse hplip.