Opening the new SOP such as Chain etc generates the error below. Does someone know how to fix it?

ERROR
Traceback (most recent call last):
File “<stdin>”, line 1, in <module>
File “C:/PROGRA~1/SideFX/HOUDIN~1.351/houdini/python2.7libs\viewerstate\utils.py”, line 476, in sceneViewerFromPath
raise hou.Error(“Could not create a scene viewer with path: %s” % pane_path)
Error: Could not create a scene viewer with path: Build.panetab1

Try clearing your H18.5 prefs folder (C:\Users\user\Documents\houdini18.5) and see if that helps. It does sound like a bug however. I could imagine that it's a bug with custom desktops or similar.

I was getting the same error and clearing my prefs fixed it.