Fix (hopefully) another threadign bug, reported by Jorgen.

IPython/Shell.py

@@ -4,7 +4,7 b''
 All the matplotlib support code was co-developed with John Hunter,
 matplotlib's author.
 
-$Id: Shell.py 1297 2006-05-13 19:14:48Z fperez $"""
+$Id: Shell.py 1313 2006-05-19 17:48:41Z fperez $"""
 
 #*****************************************************************************
 #       Copyright (C) 2001-2006 Fernando Perez <[e-mail]>
@@ -361,8 +361,11 b' class MTInteractiveShell(InteractiveShell):'
                 code_to_run = self.code_queue.get_nowait()
             except Queue.Empty:
                 break
+            if got_lock:
             self.thread_ready.notify()
             InteractiveShell.runcode(self,code_to_run)
+            else:
+                break
             
         # We're done with thread-protected variables
         if got_lock:
@@ -372,8 +375,9 b' class MTInteractiveShell(InteractiveShell):'
 
     def kill (self):
         """Kill the thread, returning when it has been shut down."""
-        self.thread_ready.acquire(False)
+        got_lock = self.thread_ready.acquire(False)
         self._kill = True
+        if got_lock:
         self.thread_ready.release()
 
 class MatplotlibShellBase: