ubuntu-bug does not exit after reporting bug / launching browser

Binary package hint: apport

When reporting a bug using "ubuntu-bug" on Kubuntu, the program does not exit after launching the browser.
It even still does exit after closing all firefox instances (Firefox has been running before).

$ ubuntu-bug python-wxgtk2.6
kfmclient(13052) ClientApp::doIt: Creating ClientApp
kfmclient(13052) ClientApp::createNewWindow: Using external browser "!firefox"

When pressing Ctrl-C it exits as follows:
^CTraceback (most recent call last):
  File "/usr/share/apport/apport-qt", line 323, in <module>
    app.run_argv()
  File "/usr/lib/python2.5/site-packages/apport/ui.py", line 325, in run_argv
    return self.run_report_bug()
  File "/usr/lib/python2.5/site-packages/apport/ui.py", line 314, in run_report_bug
    self.file_report()
  File "/usr/lib/python2.5/site-packages/apport/ui.py", line 584, in file_report
    self.open_url(url)
  File "/usr/lib/python2.5/site-packages/apport/ui.py", line 463, in open_url
    (pid, status) = os.wait()
KeyboardInterrupt

ProblemType: Bug
ApportLog:
 apport (pid 13555) Tue Mar 3 20:40:24 2009: called for pid 12675, signal 11
 apport (pid 13555) Tue Mar 3 20:40:24 2009: executable: /usr/lib/firefox-3.0.6/firefox (command line "/usr/lib/firefox-3.0.6/firefox")
 apport (pid 13555) Tue Mar 3 20:42:42 2009: wrote report /var/crash/_usr_lib_firefox-3.0.6_firefox.1000.crash
Architecture: i386
DistroRelease: Ubuntu 9.04
NonfreeKernelModules: nvidia
Package: apport 0.138
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=
 PATH=(custom, user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: apport
Uname: Linux 2.6.28-8-generic i686