Yeah I was having these issues too on OSX Mavericks and Yosemite. I tried to plug in things in the right order etc.. I would lose connectivity every time!
It was the most frustrating feeling having to hurry and export your sounds because you didn't know when the comp was going to lose connection with the synth.
I purchased a belkin thunderbolt hub off of eBay for $89 US and this has solved the problem. it was a small price to pay for stability, IMHO
Thank goodness... I was worried that I wasn't going to be able to use the software interface.
I hope this helps other Virus Users.