I have seen some of those symptoms on Win 7 64-bit, with Opera stable updates usually applied on the day released. This has happened three or four times in the last couple of weeks.
The page navigation gets into a confused state. Backwards, forwards and clicking on speed dial links takes me to the wrong URL though it will be somewhere in the recent history. Opening a fresh tab does not help but restarting Opera clears it. I use rocker gestures quite a lot, that may be of relevance. I have not spotted what exact action can trigger my problem.