Try to remove (or rename) /home/user/.opera and reinstall.

I installed Opera 11 beta 7 as well via the Application Manager on my N810. No problems, but only a few differneces.
The html5test.com site scores 193, the onscreen keyboard works now in input fields, but the URL can be entered only by the opera keyboard.
What still is a bug is that when entering http://localhost/blabla.... ( I have lighttpd running) still requires an internet connection. Other browsers (MicroB and Tear) do not require an internet connection in localhost..