[ubuntu] Default Browser Not Opening Links Clicked on in Other Applications

OS is Ubuntu 14.04. Until Yesterday I had Firefox set as my default browser. If someone were to say email me a link, then when I'd open my email (Thunderbird) and click on the link the person had sent me, my Firefox would automatically come on top in my screen, and open the link I'd clicked on. I have a lot of important works going on in Firefox, so I downloaded and set up Opera this moing, and set it as my default browser to use for simple tasks, general browsing etc. The problem I am facing now is this: although Opera is set as the default browser, when I for example click on a link in TB email, the Opera icon on the left side of my screen "wiggles", but doesn't come on top. And if I click on the Opera icon to bring it on top, it hasn't imported the link I'd clicked on. So I have to go back into my email, copy the link, and paste it into Opera. How can I automate this the way it was working in Firefox earlier-- i.e so that when I click on a link in my email, Opera will automatically come on top in my screen, and open the link I'd clicked on.