Its usual practice to RDP to a Virtualcenter box and then access the Console of Virtual Machines. However today I had a customer where when they went to the console screen of the VMs it just was black. No image was drawn at all.
Restarting the Virtualcenter server and the ESX servers did not resolve the matter.
The solution in the end was to increase the colour depth of the RDP session. With 256 Colours the Console screen is not drawn. Never knew that.