Looks good to me. I think we can safely say that GetInterfaceMethod probably works alright. I really wonder why HookAPI fails. Can you check again whether you really don't get a GetLastError value? You need to be careful not to call any win32 APIs after calling HookAPI and before calling GetLastError, because any API you're calling could clear the GetLastError value. Also avoid any string conversions, they may also clear the GetLastError. Ideally, do something like this:
No, we are not able to intercept IE9 text. Right now we are not much working on text out issues.
Once we have a time i will provide demo as requested by Madshi about my work for further troubleshooting.