Since the Release of ESX 3.5, there is a new file called /etc/vmware/configrules .
This file defines rules in a regex format to determine if a path can be accepted or not.
In this instance, the virtual machine is mapped to an ISO located at /vmbuild/GEOS46_FACTORY.iso and there is no rule in Virtual IDE Devices to allow this pattern.
To resolve the issue, edit /etc/vmware/configrules and add the following rule to the Virtual IDE Devices section, just above accept !prefix "/" :
accept prefix_case "/vmbuild/"
The virtual machine starts on the next power on.