Well I had no help from ESO, but fixed the problem myself; What happened was corruption of my client files caused by crashes in Cyrodiil. Of course I had earlier attempted to de-install and re-install the game, but no doubt to save server download time, the ESO de-installer/installer practically removes and replaces nothing on your hard disk, unless you use sophisticated "wipe" tools to clear your disk. So the files stayed corrupted. However there is a repair function on the launcher screen, hard to find under game options, that will take the time to analyse your files, replacing corruption and downloading patches as needed. That did the trick.
