I know the rules state problems shouldn't be submitted via reviews, but the support site no longer exists.
As far as I can tell Interclue works perfectly through FFox33 - and I consider it to be one of the half-dozen most important addons I use. It probably saves me an hour/day to say nothing of reducing the mousing my poor RSS fingers endure.
However, starting in FFox34, the icon option that pops up next to a link - and on which one clicks if one wants a preview - no longer appears reliably. (Indeed, it would be more accurate to say that it very rarely appears, at least on all the different web pages I use it on.) It is still possible to use Interclue by changing the option from "icon" to "link", but the problem there is timing. If you make the "time until the preview appears" too short, it will appear whenever one hovers, no matter how briefly, over every link and even every tab. If one makes it too long, so that it doesn't appear all the time, it means waiting when one wants a preview.
I've tried unsuccessfully to contact the developer. I do not know his situation, but if anybody can reach him, please do so.
Alternatively, maybe a developer would be interested in taking over the project. This is truly an exceptional addon.