We've got some user feedback regarding problems with Yosemite upgrade.
The typical issue is that the CopperLan network is still OK but MIDI handling and other settings become dysfunctional.
After some research, we've found that the problem is due to (non-CopperLan) drivers that are incompatible with Yosemite. One example of such driver is Avid's Coreaudio, which is locking the MIDI services, part of MacOS.
There might some other faulty drivers that we don't know about.
The solution is to de-install the faulty drivers, and/or upgrade them with adequate versions.
The current version of CopperLan is compatible with Yosemite.