Virtual Machine no longer loads after host upgrade from 10.9 Mavericks to 10.10 Yosemite

I was successfully using Parallels 10.4.0 on Mavericks OS X 10.9. I foolishly upgraded to Yosemite OS X 10.10.5 after verifying that Parallels 10 would run on Yosemite. My bad for upgrading my OS...
I was running Snow Leopard Server 10.6.8 as my virtual machine in order to run Macromedia (Adobe) Freehand.
I must get up and running again. Can anyone help me please? My customers are waiting for their artwork and I have no idea how to fix this issue.
The error message is: "The virtual machine cannot be started".
I've changed nothing except to upgrade my host OS from 10.9 to 10.10. My virtual machine (10.6.8) is a legal copy of Snow Leopard Server. I've been using parallels in coherence mode for over two years without a problem.
Thanks
Stuart

 

Please, send us a problem report:
0. start Parallels Desktop;
1. try to start virtual machine - get error probably;
2. in the virtual machine's application menu bar press Help -> Report a Problem...
3. post report id here.