That’s right, in my Firefox – it was never a problem in most other people’s Firefoxes. I’d been having problems with it for many years, in various versions of Firefox and on several different computers. I’m thinking I might even have had this problem when I was still running Linux on my main machine. Not just Google Maps, also Live Maps and a few other mapping sites. Weird, yes, but somehow it never seemed important enough to look into – I just used IE instead and it worked in there.
Anyway, I finally hunted it down and as usual the answer is simple once you know it. There was a setting in the prefs.js file in my profile:
user_pref("dom.disable_image_src_set", true); Got rid of the line, now everything works. Great, eh?