Internet explorer doesn't open websites by using wptdriver 2.11

[cws]

Unfortunately, updating wptdriver to version 2.12 hasn't fixed the problem. IE still just opens and doesn't navigate to the page. I think the problem might be caused since the IE extension isn't loaded correctly. Thus, I inspected the loaded dlls of the started IE instance (by using ProcessExplorer). It says that "wptglobal.dll" is loaded but there is no "wptbho.dll" in the loaded dlls of the iexplore process.

Is there anything else (like e.g. registry entries or something like this) that I have to configure for using wptdriver with IE 9 on windows 7 x64?