If you are using O2's REPL environment to write IE scripts, you really should change your environment to use the latest version of IE inside the C# .NET Control (or else you will be using IE 6 or 7 which is just about unusable in today's web world)
This is the O2 Script that does that: Set .NET WebBrowser Control to use latest version of IE
Once that is executed, you should get IE 9 inside O2: