What can cause Intellij to suddenly become very slow with scala?

I have been using Intellij 12 to create a Play Framework 2 application for about a month. That was good until yesterday. Now when I try to write code in one of the scala templates, Intellij becomes very very slow. For example, it takes 5-10 seconds to enter a couple of new lines. What can lead to the fact that it will start suddenly and how to fix it?

I tried to increase my vm parameters to the following, but this did not help:

-Xms256m
-Xmx800m
-XX:MaxPermSize=512m
-XX:ReservedCodeCacheSize=128m
-XX:+UseCodeCacheFlushing
-XX:+UseCompressedOops

Edit: can a recent Intellij or plugin update kill performance?

Edit: I updated my scala and Play plugins, and that didn't help.