Ran into this while running Vmware Workstation under Ubuntu Jaunty. I got an error while shutting down the machine through an NX session.
This is a result of a zombie 'vmware-vmx' process running. All you need to do is kill the process. This command sends 'signal 9' to the process. When sent to a program, SIGKILL causes it to terminate immediately. In contrast to SIGTERM and SIGINT, this signal cannot be caught or ignored. For more information: more sigkill info.
killall -s9 vmware-vmx
After that, I was able to start up the virtual machine without issue.