No more JACK-rack on my raspbian.

Hello all. Please can someone help. I have a Pi 2 with Jessie installed. I want to use Jackctl and JACK-rack as a lowpass x over dsp for my sub. All loads fine, so I plug in my Behringer UCA202 usb low latency soundcard and Jackctl is fine, but JACK-rack won't load. It tries by displaying a white box where the logo usually is then dissappears! I did have it running a while back on an pi B+ and it was unstable, so I bought the improved Pi2 and still no joy???
If I can't get this to work, Ecasound and the Steve Harris plugs will my only choice, but I'd rather JACK-racks easy gui.
Thanks Mike