My suggestions are;
1. Uninstall all previous versions of eclipse and reinstall the Eclipse 3.5.
2. Please check the IP address of VMware Studio in the link given in step #3 from procedure*
3. I am not sure but while installing plugin, it might ask you to install dependencies. So please check the browser properties to download the files. It seems dependency problem. So recheck step#3 from procedure*
4. Please restart the Eclipse after installing plugins
5. Please check JDK is installed or not.