I think there has been a problem with C6 since Mountain Lion. Never had problem using Snow Leopard (and never used Lion, but maybe then).

Try setting the delay ticks higher, maybe 5 to start, and go up from there. I’ve had to set it to at least 10, maybe higher, or it will fail to properly send data. The problem is that it will take much longer to send data the more delay you add.

I hope Elektron can find some time to update C6 soon. There have been a number of threads about it having faults recently.