I think I may have found what has been causing my problems.
I remember now that I installed one of the extra utility programs Epsom offer in "Software updater"
It was the one called "Epson Web print" and I found it useful because it lets you select any rectangle on a web page and clip/print it.
It was soon after that that scanning stopped working.
So i had uninstalled everything with Epson in the name, drivers and printers, and re-installed from scratch with latest SW from Epson.com
Then everything worked fine.
Today I had use of the web print utility so I installed "Epson Web print" again
Now the Epson Scan program doesn't start.
I guess I'll have to re-install everything again... this time I won't install Epson Web print at all.