I recently installed Windows 8 on a laptop, as well as VMware workstation 9. Later on, I added Hyper-V roles. When I tried to power Workstation back up, I got the following error message:
VMware Workstation and Hyper-V are not compatible. Remove the Hyper-V role from the system before running VMware Workstation.
Removing the Hyper-V role, entirely, seems to suffice. I tried removing the Hyper-V role and shutting down the Hyper-V management service without rebooting, but that did not help. After rebooting, the Hyper-V management service was gone and VMware Workstation could launch VMs properly again.