To further debug what is going on here, first step:
Run sound-juicer from the command line
Try to get the bug to reproduce after you run it from the command line, and hopefully you will see more output show up in the terminal where you ran it.
# First open up 'gnome-terminal', then
$ sound-juicer
If that doesn't get you any more info...
Check common log files
- General errors:
/var/log/syslog
- Kernel/Hardware errors: run the command
dmesg
- Kernel/Hardware errors:
/var/log/kern.log
Next...
Run sound-juicer from the command line with debug options
$ sound-juicer --help-all |grep -i debug
--gdk-debug=FLAGS GDK debugging flags to set
--gdk-no-debug=FLAGS GDK debugging flags to unset
--gtk-debug=FLAGS GTK+ debugging flags to set
--gtk-no-debug=FLAGS GTK+ debugging flags to unset
--brasero-media-debug Display debug statements on stdout for Brasero media library
--gst-debug-help Print available debug categories and exit
--gst-debug-level=LEVEL Default debug level from 1 (only error) to 9 (anything) or 0 for no output
--gst-debug=LIST Comma-separated list of category_name:level pairs to set specific levels for the individual categories. Example: GST_AUTOPLUG:5,GST_ELEMENT_*:3
--gst-debug-no-color Disable colored debugging output
--gst-debug-color-mode Changes coloring mode of the debug log. Possible modes: off, on, disable, auto, unix
--gst-debug-disable Disable debugging
Looking at that list and the text of the error pop up, I'd start with
$ sound-juicer --gst-debug=all
And proceed from there. Once I reproduced it, perhaps with all the debug flags turned, on, and it was clear this was not a setup problem, or problem with something you did configuration-wise. I would...
File a bug on sound-juicer upstream
Look in their bug tracker, and file away! You can also file a bug in launchpad, but make sure to reference the upstream bug when you file. You can also go the other way around and use ubuntu-bug sound-juicer which would make a nice first start in launchpad, but don't be shy and leave the issue there, inform the upstream devs of the issue too.
More info
See here for some general tips on running gtk apps with debug flags.