Check to make sure that your not getting any kind of selinux denial in /var/log/audit/audit.log and /var/log/messages. Also check for lock files in the virtual machines directory. The error window in the GUI does not give very useful error messages at all.
I'm having the same problem. It was working fine (in RC1), then, for no reason that I can ascertain, the VM's fail to even start. It jumps to 95% completion, then stops. It also dedicates the RAM to the VM, and the only way to get it back is to restart my machine. I've tried deleting the VM's and creating new ones, repairing the installation, uninstalling and reinstalling, and connecting to the site differently. All resulted in the same problem. I'm currently running Vista Home Premium x64, with 2GB DDR2 800, and Intel Core 2 Duo E6420. My thought is that 64-bit drivers are still a little flaky.
Same problem here too. Vista 64 Ultimate Intel Q6600 cpu. Vms hangs at 95%. Only solution is to reboot the host. So Vmware server is unusable. First time I installed it worked ok. Now hangs....