As originally reported ​here on the mailing list, here is the backtrace obtained with abrt.

Note: contrary to the report above, when I test this only happens on KDE, and only when using "auto-start".

abrt_version:   2.0.10
cmdline:        /usr/bin/python /usr/bin/winswitch_applet --open_server_config=
executable:     /usr/bin/winswitch_applet
kernel:         3.5.2-1.fc17.x86_64
time:           Wed 29 Aug 2012 11:30:08 PM ICT
uid:            1000
username:       fedora

backtrace:
:warnings.py:29:_show_warning:ValueError: I/O operation on closed file
:
:Traceback (most recent call last):
:  File "/usr/lib/python2.7/site-packages/winswitch/client/client_base.py", line 744, in server_dir_changed
:    self.slog("evt_type=%s" % type(evt_type), monitor, d, ignored, evt_type)
:  File "/usr/lib/python2.7/site-packages/winswitch/util/simple_logger.py", line 317, in slog
:    self._write(self.log_colour, "II", self.prefix, msgsig(msg, *args))
:  File "/usr/lib/python2.7/site-packages/winswitch/util/simple_logger.py", line 231, in msgsig
:    s = msig(*args)
:  File "/usr/lib/python2.7/site-packages/winswitch/util/simple_logger.py", line 214, in msig
:    return	"("+(','.join([str(v) for v in args]))+")"
:  File "/usr/lib64/python2.7/warnings.py", line 29, in _show_warning
:    file.write(formatwarning(message, category, filename, lineno, line))
:ValueError: I/O operation on closed file
:
:Local variables in innermost frame:
:category: <class 'gobject.Warning'>
:filename: '/usr/lib64/python2.7/site-packages/twisted/internet/gtk2reactor.py'
:lineno: 277
:file: <closed file '/home/fedora/.winswitch/client/applet.log', mode 'a' at 0x7fdde6333f60>
:line: None
:message: Warning("g_object_set_qdata: assertion `G_IS_OBJECT (object)' failed",)

The gpg key at ​https://winswitch.org/gpg.asc used e.g. by the Debian / Ubuntu repos has expired:

$ curl -s  https://winswitch.org/gpg.asc  | gpg -

pub  1024D/F18AD6BB 2007-04-18 Antoine Martin <[email protected]>
uid                            [jpeg image of size 4992]
sub  2048g/6E23E963 2007-04-18 [expires: 2018-05-04]

leading to errors when one runs apt-get update:

Err:17 http://xpra.org xenial Release.gpg
  The following signatures were invalid: KEYEXPIRED 1525416977  KEYEXPIRED 1525416977  KEYEXPIRED 1525416977

This was mentioned in #198 but it seems like it was overlooked.

NXAGENT - Version 3.5.0

Copyright (C) 2001, 2011 NoMachine.
See http://www.nomachine.com/ for more information.

Info: Agent running with pid '8227'.
Session: Starting session at 'Wed Oct  3 00:44:12 2012'.
Error: Aborting session with 'Unable to open display 'nx/nx,options=/home/me/.winswitch/server/sessions/72/nx_options.txt:72''.
Session: Aborting session at 'Wed Oct  3 00:44:12 2012'.
Session: Session aborted at 'Wed Oct  3 00:44:12 2012'.

Why is all that extra stuff being sent to NX for the display, instead of it just being ":72"?

winswitch:
  Installed: 0.12.16-4
  Candidate: 0.12.16-4
  Version table:
 *** 0.12.16-4 0
        500 http://winswitch.org/ precise/main i386 Packages
        100 /var/lib/dpkg/status