I had checked, and unchecked, the box (repeatedly) and still no error, so now I've tried all browsers and of course it's IE that has the problem, as usual.
I'll check it out - maybe a basehref issue or IE's handling of javascript.
I neglected to delete the Resources link when I removed it after I updated Storez content (Resources was my old custom built ebook store) - fixed, thanks.
Edit:
Adjusted to compensate for IE's handling of the link.
Probably should have spotted that long ago - IE has always treated inline js differently to all other browsers