That message can appear for many reasons. To start troubleshooting, let's collect get some basic information: Which VMware product are you using (VMware Workstation, VMware Fusion) and which version are you using? Which operating system are you running on the host system and inside the virtual machine?
Usually when a virtual machine fails there will be a log file named vmware.log created inside the virtual machine's folder/directory. If you can find that file, providing it with your reply would also assist with troubleshooting. (Just look for the Attach link in the lower-right corner of the editor window when composing your reply.)