Created attachment 488036 [details]
File: backtrace

Package: pitivi-0.13.5-4.fc14
Architecture: i686
OS Release: Fedora release 14 (Laughlin)


How to reproduce
-----
1.
2.
3.
.

Can try :

rm -rf ~/.gstreamer-0.10


and see if the issue persists ?

pitivi-0.14.0-2.fc14 has been submitted as an update for Fedora 14.
https://admin.fedoraproject.org/updates/pitivi-0.14.0-2.fc14

Package pitivi-0.14.0-2.fc14:
* should fix your issue,
* was pushed to the Fedora 14 testing repository,
* should be available at your local mirror within two days.
Update it with:
# su -c 'yum update --enablerepo=updates-testing pitivi-0.14.0-2.fc14'
as soon as you are able to.
Please go to the following url:
https://admin.fedoraproject.org/updates/pitivi-0.14.0-2.fc14
then log in and leave karma (feedback).

This package has changed ownership in the Fedora Package Database.  Reassigning to the new owner of this component.

This package has changed ownership in the Fedora Package Database.  Reassigning to the new owner of this component.

This package has changed ownership in the Fedora Package Database.  Reassigning to the new owner of this component.

pitivi-0.14.0-2.fc14 has been pushed to the Fedora 14 stable repository.  If problems still persist, please make note of it in this bug report.

I'm experiencing this problem as well.

Fedora 14

$ rpm -qa pitivi
pitivi-0.14.0-2.fc14.noarch

$ rpm -qa gst*
gstreamer-plugins-bad-free-0.10.20-3.fc14.x86_64
gstreamer-plugins-base-0.10.31-1.fc14.x86_64
gstreamer-plugins-ugly-0.10.16-2.fc14.x86_64
gstreamer-python-0.10.19-1.fc14.x86_64
gstreamer-ffmpeg-0.10.11-1.fc14.x86_64
gstreamer-tools-0.10.31-1.fc14.x86_64
gstreamer-rtsp-0.10.5-2.fc14.x86_64
gstreamer-plugins-good-0.10.26-1.fc14.x86_64
gstreamer-0.10.31-1.fc14.x86_64

$ ls /usr/lib64/gstreamer-0.10/libgstvideomixer.so
/usr/lib64/gstreamer-0.10/libgstvideomixer.so


$ pitivi
** Message: pygobject_register_sinkfunc is deprecated (GstObject)
Traceback (most recent call last):
  File "/usr/bin/pitivi", line 143, in <module>
    _run_pitivi()
  File "/usr/bin/pitivi", line 138, in _run_pitivi
    sys.exit(ptv.main(sys.argv))
  File "/usr/share/pitivi/python/pitivi/application.py", line 530, in main
    ptv = StartupWizardGuiPitivi(debug=options.debug)
  File "/usr/share/pitivi/python/pitivi/application.py", line 383, in __init__
    self.projectManager.newBlankProject()
  File "/usr/share/pitivi/python/pitivi/projectmanager.py", line 186, in newBlankProject
    track = Track(video)
  File "/usr/share/pitivi/python/pitivi/timeline/track.py", line 997, in __init__
    self.mixer = self._getMixerForStream(stream)
  File "/usr/share/pitivi/python/pitivi/timeline/track.py", line 1091, in _getMixerForStream
    m = SmartVideomixerBin(self)
  File "/usr/share/pitivi/python/pitivi/elements/mixer.py", line 130, in __init__
    self.videomixer = gst.element_factory_make("videomixer", "real-videomixer")
gst.ElementNotFoundError: videomixer


I clearly have the library in question, but the element_factory_make doesn't seem to be able to find it.

(In reply to comment #10)
> I'm experiencing this problem as well.
> 
> Fedora 14
> 
> $ rpm -qa pitivi
> pitivi-0.14.0-2.fc14.noarch
> 
> $ rpm -qa gst*
> gstreamer-plugins-bad-free-0.10.20-3.fc14.x86_64
> gstreamer-plugins-base-0.10.31-1.fc14.x86_64
> gstreamer-plugins-ugly-0.10.16-2.fc14.x86_64
> gstreamer-python-0.10.19-1.fc14.x86_64
> gstreamer-ffmpeg-0.10.11-1.fc14.x86_64
> gstreamer-tools-0.10.31-1.fc14.x86_64
> gstreamer-rtsp-0.10.5-2.fc14.x86_64
> gstreamer-plugins-good-0.10.26-1.fc14.x86_64
> gstreamer-0.10.31-1.fc14.x86_64
> 
> $ ls /usr/lib64/gstreamer-0.10/libgstvideomixer.so
> /usr/lib64/gstreamer-0.10/libgstvideomixer.so
> 
> 
> $ pitivi
> ** Message: pygobject_register_sinkfunc is deprecated (GstObject)
> Traceback (most recent call last):
>   File "/usr/bin/pitivi", line 143, in <module>
>     _run_pitivi()
>   File "/usr/bin/pitivi", line 138, in _run_pitivi
>     sys.exit(ptv.main(sys.argv))
>   File "/usr/share/pitivi/python/pitivi/application.py", line 530, in main
>     ptv = StartupWizardGuiPitivi(debug=options.debug)
>   File "/usr/share/pitivi/python/pitivi/application.py", line 383, in __init__
>     self.projectManager.newBlankProject()
>   File "/usr/share/pitivi/python/pitivi/projectmanager.py", line 186, in
> newBlankProject
>     track = Track(video)
>   File "/usr/share/pitivi/python/pitivi/timeline/track.py", line 997, in
> __init__
>     self.mixer = self._getMixerForStream(stream)
>   File "/usr/share/pitivi/python/pitivi/timeline/track.py", line 1091, in
> _getMixerForStream
>     m = SmartVideomixerBin(self)
>   File "/usr/share/pitivi/python/pitivi/elements/mixer.py", line 130, in
> __init__
>     self.videomixer = gst.element_factory_make("videomixer", "real-videomixer")
> gst.ElementNotFoundError: videomixer
> 
> 
> I clearly have the library in question, but the element_factory_make doesn't
> seem to be able to find it.

Did you try what is in comment 3

Look at 

http://gstreamer.freedesktop.org/data/doc/gstreamer/head/faq/html/chapter-troubleshooting.html 

for general troubleshooting suggestions for applications using gstreamer.

(In reply to comment #11)
> (In reply to comment #10)
> <snip>
> 
> Did you try what is in comment 3

Yes.  Same result.