Ubuntu 14.04 LTS Arduino IDE becomes unstable when connected to Arduino board

Hi All,

I have a new installation of Ubuntu 14.04 LTS. The Arduino IDE becomes unstable and unresponsive as soon as I connect any arduino board via USB. This seems to be a problem with librxtx but I'm not sure the best way to fix. Any advice on fixing the problem is much appreciated.

I can upload sketches with AVRISP mk2 without problems.

Thanks