I upgraded my Scala plug-in, relaunched IDEA and opened my all-Scala project. The first thing I noticed was that some names were not properly highlighted (they were black, not the color I'd assigned for them). I thought perhaps the Scala coloring categories had changed, so I wanted to open the Options dialog to check them out. As soon as I clicked on the Settings icon in the toolbar, IDEA deadlocked (would not respond or redraw any of its UI and one-per-second thread-dumps were being created). One of those thread-dumps is attached.
When I relaunched IDEA and reopened my project, the highlighting I'd previously noted as wrong was correct.
IDEA: 8.1.3 #9886
Java: Sun JDK 1.6.0_u15
OS: Linux; kernel: 18.104.22.168-0.1-pae
GUI / Desktop: KDE 3.5.10
Distro: openSUSE 11.1