I recently had the same problem and it was because I had a previous version of tomcat installed, upgraded to a newer version, deleted to old one, and never changed the runtime environment in Eclipse. It's kind of a poor error message because it doesn't state the true nature of the problem but anyway... The easiest way to fix this is:
Open Eclipse, right click on the workspace and select New Server.
Once you are at the Define New Server wizard click on Apache and select Tomcat 6. This is where you should see the error The currently selected server type does not support remote hosts. Now below server runtime environment click Configure Runtime Environments and new popup will open. You should see Apache Tomcat v6.0 in the preferences window. Select this and click edit to the right.
You will have a new popup titled Edit Server Runtime Environment. Under Tomcat Installation Directory you can browse to the location of the tomcat directory. Assuming you have downloaded Tomcat and put it at the top level of your C: drive you should have something like this: C:\apache-tomcat-6.0.36. Click finish and you should be good to go. Let us know how it works out for you!