Hi,
For a live show, i am using :

-a 2 months old Macbook pro running Yosemite,
-Ableton Live, registered user, all recent updates,
-RME UC Fireface, brand new USB sound card with MIDI i/o, the driver and the software are up to date
-keyboard connected to RME UC via MIDI,
-Other devices such as Korg Nanokey and similar, USB connected to the Mac, through a USB Hub

3 times this month, the RME UC Fireface interface interrupted its communication with the computer, during a show or between the soundcheck and the show.

The sound card was appearing in the audio setup of Ableton LIve but with no reaction on the Ableton Live bargraphs nor on the RME virtual Mixer TotalMix when playing on the master keyboard or on any other device.

I had to relaunch the computer to make the gear work properly.
I am very familiar with this equipment, I've been using Macs, RME (Fireface800 usually) and that kind of gear for more than ten years but never met that kind of issues.

I'm sending this message to Ableton support and RME support at the same time.

Any suggestion will be more than welcome.
Thank you in advance.
Quetz