Running Eclipse 4.2 with TeXclipse 1.5.0 plugin enabled suffers from similar AST freezes as described some time ago. They occur in Java editor. While those older descriptions talked about freezing on Ctrl, Ctrl+C or Ctrl+V, my bugreport is about freezing upon proposal request (Ctrl+Space). After disabling TeXlipse the problems are gone.
I attach 2 thread dumps from different types of freezeup.