So I installed and played about with Gnuradio after seeing a talk at defcon london this month.
Some little trips i found along the way and their fixes!
GRC (gnu radio companion) wont start - copy your grc.conf file to yourlocal directory, you might need to make the .gnuradio folder first.
cp /etc/gnuradio/conf.d/grc.conf ~/.gnuradio/config.conf
GRC now works but audio sinks dont like your sound card under ubuntu, this is because your running pulse audio not alsa...and so it cant open the device, so to solve this set the device name in the sink to "pulse" and set the sample rater to 48Khz
if i find more problems ill add to this post.