I'm using ESXi 6.0 with 6 VMs. 4 Windows 7 and 2 Windows 2008 R2. When I first connect through vSphere everything is ok, I can switch between the VMs and everything is fine. After vShere has been logged in for a couple of hours and I switch to a VM I've not looked at for a while the screen is black and I have to right click on the VM to 'Open Console' to allow me to view it (this doesn't always work).
I have checked the VMs and ESXi are all using the same DNS server config, all VMTools are up to date and no firewalls are in place. Has anybody seen this before and can offer any help?