I have set Google Chrome as my default browser. I update to every test build released by the Opera Desktop Team and almost all of the recent builds made Opera the default browser on my system.
This bug was fixed a while ago. Opera checks for the default browser setting on the system. If it is set to a competing browser, it would not turn this feature on.

But Opera 11.10 and all the RC editions had the default browser setting on by default. Very annoying.
