Comment 2 for bug 430697

I've finally found out why this happens. The two processes use the Tk send function to communicate with each other which only worls, when the xhost list is empty. For some reason, my xhost list wasn't empty but contained these entries:

bodo@sakura:~$ xhost
access control enabled, only authorized clients can connect
SI:localuser:bodo
SI:localuser:gdm
SI:localuser:root

These entries are added by /etc/X11/Xsession.d/60x11-common_localhost contained in x11-common.

bodo@sakura:~$ apt-cache policy x11-common
x11-common:
  Installed: 1:7.4+3ubuntu10
  Candidate: 1:7.4+3ubuntu10
  Version table:
 *** 1:7.4+3ubuntu10 0
        500 http://de.archive.ubuntu.com karmic-updates/main Packages
        100 /var/lib/dpkg/status
     1:7.4+3ubuntu7 0
        500 http://de.archive.ubuntu.com karmic/main Packages