Source Editor tool totally erases my sources.list file

Sorry to here that, I should provide a backup feature to source editor.

En ubuntu 8.0.4.2 LTS descargado de los repositorios pp's (tualatrix) y de getdeb al pasar a "fuentes de terceros" solicita actualizar los mismos y al hacerlo los elimina de "sources.list", en terminal da los siguientes errores

xxxxxx@xxx:~$ ubuntu-tweak
/usr/lib/python2.5/site-packages/apt/__init__.py:18: FutureWarning: apt API not stable yet
  warnings.warn("apt API not stable yet", FutureWarning)
Traceback (most recent call last):
  File "/usr/share/ubuntu-tweak/thirdsoft.py", line 459, in check_ppa_entry
    self.do_update_ppa_entry()
  File "/usr/share/ubuntu-tweak/thirdsoft.py", line 491, in do_update_ppa_entry
    if proxy.edit_file(SOURCES_LIST, '\n'.join(lines)) == 'error':
  File "/var/lib/python-support/python2.5/dbus/proxies.py", line 68, in __call__
    return self._proxy_method(*args, **keywords)
  File "/var/lib/python-support/python2.5/dbus/proxies.py", line 140, in __call__
    **keywords)
  File "/var/lib/python-support/python2.5/dbus/connection.py", line 607, in call_blocking
    message, timeout)
dbus.exceptions.DBusException: org.freedesktop.DBus.Python.UnicodeEncodeError: Traceback (most recent call last):
  File "/var/lib/python-support/python2.5/dbus/service.py", line 696, in _message_cb
    retval = candidate_method(self, *args, **keywords)
  File "/usr/sbin/ubuntu-tweak-daemon", line 144, in edit_file
    file.write(content)
UnicodeEncodeError: 'ascii' codec can't encode character u'\xed' in position 3216: ordinal not in range(128)

Thank you very much about the output! It's really helpful to me.

I will fix it as soon as possible.