After upgrading to plug-in 0.3.1845 (and a longish re-indexing the first time I opened my project), IDEA reported this:
(!) Error Loading Project
Cannot load facet Scla (rho) Details...
Clicking details presents a small alert stating:
(X) Unknown facet type: 'Scala'
Would you like to remove facet 'Scala' from module 'rho'?
(I chose "No")
I quit, relaunched and reopened my project, but while the indexing did not happen the second time, the alert appeared again.