We've been noticing a lot of freeze-ups in IntelliJ since version 11. This happens in Ubuntu 11.10 and Windows 7.
Today I've had another freeze-up, and after googling around tried upgrading the JDK from 126.96.36.199 to 1.7.0_02. IntelliJ hung again after a few minutes.
I'm attaching the first thread dump from the JDK6 freeze, and also the first from the JDK7 freeze.
We're using the Play! Framwork, so it might be related.