Hi Paul,
Got this dreaded issue again. I will send you the journal file. It's on the latest 'debug' version of the plugin.
Again, I am on Win 8 / Revit 2014.
Activity involved creating a conceptual mass outside of the model when the plugin was not running. It was, however, running earlier. I got the following error when inserting the family into my Revit model - even though the plugin was not running at that time. It was late at night but I think it was after this that the model had lost the materials & proxies.
Best,
Hendrik