This problem was identified a while ago, right after Z-Wave support was added to Indigo. Sometimes, like a power failure, or a crashed system, or at times, even a regular re-boot, the device name for the Z-Stick changes. I always have a /dev/tty.SLAB_USBtoUART and then another /dev/tty.SLAB_USBtoUARTn. The correct interface device is usually the one ending in the integer.
Anyway, the question is, has anyone come up with a fix or a work around for this problem? If there was one discussed, I guess I missed it. In that case, could someone point me to the thread.
BTW, I have just now upgraded to the latest driver with the installer dates 16-January-2014. Though the read me says CP210x Macintosh OSX VCP Driver v3.1 - December 6, 2012. If this is supposed to address this problem I guess I'll figure it out soon enough.