Hi Daniel, I cleared the cache but it made no difference and I don't have any script errors. I ended up uninstalling and reinstalling the old version so its alll working again. Fortunately I did not lose my hotspots in the process - only lost the images assigned to the categories so it was really easy to fix.
I won't try the update from either the Hotspots or Joomla update screens just in case. The problem may well be with my host where I have a 2mb file limit. I usually overcome this by using FTP to install from my tmp folder. I'd like to do this for the new version of Hotspots but I can't seem to locate the zip file on your site.
Otherwise Hotspots is a fantastic extension - well done!