I'm experiencing a similar issue. Fresh install of 3.3 today from the .msi installer on the web site, identifies itself as:
Python 3.3.0 (v3.3.0:bd8afb90ebf2, Sep 29 2012, 10:55:48) [MSC v.1600 32 bit (Intel)] on win32

To reproduce: Copy and paste this character into IDLE. 𝐇

C:\Python33>.\python -m idlelib.idle
Traceback (most recent call last):
  File "C:\Python33\lib\runpy.py", line 160, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "C:\Python33\lib\runpy.py", line 73, in _run_code
    exec(code, run_globals)
  File "C:\Python33\lib\idlelib\idle.py", line 11, in <module>
    idlelib.PyShell.main()
  File "C:\Python33\lib\idlelib\PyShell.py", line 1477, in main
    root.mainloop()
  File "C:\Python33\lib\tkinter\__init__.py", line 1038, in mainloop
    self.tk.mainloop(n)
UnicodeDecodeError: 'utf-8' codec can't decode bytes in position 0-2: invalid continuation byte


(Incidentally, there appears to be a slight difference depending on whether I copy the character in Chrome or Firefox. IDLE terminates the same way, but a Latin-1 app sees the character from Firefox as a letter, but the same thing from Chrome is two question marks (presumably the surrogates).)