m32r - X-Live Card - lost returns from mac


I'm using mainstage with UAD Effects as my outboard effects via the X-Live card. I'm sending 4 auxes to mainstage an 1 stereo return from mainstage to the desk. At yesterdays show I lost the stereo return already at soundcheck. Only shutting down and rebooting the console solved the problem, but just for a minute, then the desk (or card) lost the stereo return again. I'm running this setup for a long time now with never any issues. The card was recognized by the computer at any times. I also was recording to the SD cards. Anybody any idea? Thanks for your replys