Using Python 3.0b3 on windows XPH SP2 (installed form python-3.0b3.msi) 
Idle can't be started.
Using a windows shortcut, only an error-promt is shown "Subprocess 
Startup Error: IDLE's subprocess dien't make connection. Either IDLE 
can't start a subprocess or personal firewall is blocking the 
connection."
I'm aware of the warning about firewalls in IDLE, but the previous 3.0 
betas didn't have that issue with the same settings of the windows 
firewall.

After directly calling:
C:\Python30\python.exe C:\Python30\Lib\idlelib\idle.py

The same error is thrown, but previously another exception is writen to 
the console:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "C:\Python30\lib\idlelib\run.py", line 76, in main
    sockthread.set_daemon(True)
AttributeError: 'Thread' object has no attribute 'set_daemon'

Regards,
   vbr

I also had problems running IDLE, and the fix listed here solved it for
me: http://bugs.python.org/issue3628

Closing as a duplicate of issue3628

Sorry for the noise, somehow my search in the bug tracker didn't show 
this report; after fixing the mentioned line in run.py everything works 
ok.