Exactly.
Geez, no need to unchek everything, just unchek Opera-Cookies on Applications tab and cleaning go smoothly.
And go for simle analysis. Check Opera-Cookies and run Filemon. It says that last accessed file before an esception was cookies4.dat.
Just moved it out from the %ProgramFiles%\Opera\profile\ and issue solved. Both System-Options-Cookies and Application-Opera-Cookies.
And what is "cookies4.dat.sbsd.bak"? It's 160Kb against "cookies4.dat" 13Kb. And moving it out from profile makes no difference.
Uploaded buggy cookies4.dat, with hope, that it will be analyzed by developers.
opera_buggy_cookies.zip