This is about Opera 12.8. I made the mistake of checking "do not show this window again" after checking "yes" to start an external program on my computer linked to by a web page. (It's an image downloader) It always worked until after I checked "do not show ..." Now it gives me the error "No registered application for this extension." I've tried searching the web. Lots of people have the problem but no solution is posted. "Check on the Opera forum!" is the usual answer. So I tried to search for the error message and various subsets of the words in in the search box in the Opera for windows forum. It always always just kicks me back to the main forum page without explanation. Hence, I have started this discussion -- although the answer is probably in the forum somewhere already.
How can I re-register the application for the extension?