The native Peer Method public int getState0____I (MJIEnv env, int objref) in class JPF_java_lang_Thread is not defined static. So the translationprocess fails to redirect calls to Thread.getState0 (and as a consequence Thread.getState()). If the method is not broken and the static definition was removed on purpose i suggest someone on the dev list fixes that.
JPF release version is 1533 from trunk
Java version is 1.6