I'm not sure that this is the best place to get support for a Revit addin (!), but couldn't see any more appropriate support channels on the Graphisoft website.
I've installed the ArchiCAD Connection addin on several workstations for Revit 2015, and on a few of them the Improved IFC Import addin just won't display or function correctly (see attached image). While it is in this state you can click on various UI elements and they may highlight but none function. The only way to get out of this is to kill the Revit process.
I've ensured that the video driver installed is one certified for Revit, and have also tried the latest driver. I've also tried turning off hardware acceleration in Revit.
So far, I just can't figure what is causing this. Any suggestions?
We came across a very rare bug with another Revit user who obtained similar freezes to yourself both on import and export which was related to the version of the .NET Framework on the computer. Could you please try downloading and installing the .NET Framework 4.5.1 from here: