OK well it seems it will be necessary for you to persist on the UHD forum.  As previously mentioned the error that you've reported is outside of OP25.

Also, when posting to the UHD forum, you might point out that, according to this page (URL below) the version of ubuntu (12.04) that you're using is listed as one of the UHD-supported ubuntu versions - they need either to fix the problem or to update the page to remove 12.04 from the supported list...

http://code.ettus.com/redmine/ettus/projects/uhd/wiki/UHD_Linux

Max