I have the same issue with Lenovo U310 (win8 64), which could not find my HDMI connected monitor of LG W2261.
IMHO, the issue may be solved by force detection mode of HD4000 driver. Could it be implemented in advanced mode?
But the same PC has no problem to detect Sony Bravia TV after restart, after that, my external monitor can be extended too! but identified as TV. Checking Device Manager, I found both internal & external displays are identified as generic PnP monitors! So I installed the driver of LG W2261, it soon identified as "W2261(HDMI)", which looks reasonable.
Up to now, no problem.
So that's my solution, hope this help you too.