I am running Parallels 12.1.1 on a 27-inch, late 2012 iMac (MacOS Sierra) with a low cost second monitor attached. Windows 7 is the guest OS. When I use Coherence mode, Windows programs run OK on the second monitor but when they open or are moved to the iMac screen they are blank. Can be either white or black. Only happens in Coherence mode. This seems to have occurred since I experimented with the Mac's split screen capability. Can someone please help.
