To reproduce the bug:
1. Open Impress, any version, I tried from 4.2 to 5.1
2. Insert -- Media. Insert an audio file.
3. Impress will hang for a minute.
4. Switch to another slide and switch back to the slide with audio. Impress will hang.
I googled for this issue and saw some people reporting that this issue appered after Ubuntu 12.04 LTS when a new version of Gstreamer had been started to be used.
MKV video files seem to work OK.
OpenOffice 4 works correctly and this issue is not reprodusible inside Apache OpenOffice
And yes it is reproduced on Linux only.
*** This bug has been marked as a duplicate of bug 81849 ***