AC 14 has been improved in several spots which you won't recognize immediately.
There are shadows in OpenGL, but also the curved surfaces are improved. This might cause a relapse in the performance with the same hardware and drivers.
First update the drivers of your videocard. If you have tried many drivers beforeuse this free tool to clean leftover drivers:
http://www.guru3d.com/category/driversweeper/
Secondly you can change the configuration back to the old AC13 way:
Set the "Enable Shaders" to 0 in the registry or preferences: HKEY_CURRENT_USER/Software/GRAPHISOFT/ArchiCAD(or)ArchiCAD-64/<ArchiCAD version>/OpenGL
HTH