UPDATE. I have a very similar problems on Ubuntu proper also, Nautilus uses 100% CPU on login and is simply unresponsive.
The common factor is that my standard home subfolders, Pictures, Videos, Downloads, Documents, Templates, Public (but not the actual home folder itself) are links to folders on a different drive.
UPDATE 2 : I have restored my normal home folders (Pictures, Downloads etc), and created links inside those folders to the folders on the other drive. The issue has gone away, no more 100% CPU usage.
I will report a bug.