What I did before is I deleted a Tomcat 7 server from Eclipse and I was trying to reinstall Tomcat 7. But it doesn't allow me to type anything in that textbox and I cannot proceed to the "Next" button. My environment is Ubuntu Linux and Eclipse for JavaEE.
Here is the workaround that worked for me:
Close Eclipse
In {workspace-directory}/.metadata/.plugins/org.eclipse.core.runtime/.settingsdelete the following two files:
org.eclipse.wst.server.core.prefs
org.eclipse.jst.server.tomcat.core.prefs
Restart Eclipse
果然有效