I have this workspace downloaded off the web and I try running it on a tomcat server from a fresh installation of Eclipse Ganymede. This particular project came with its own workspace.
When I select Tomcat v6.0 I get a message
Cannot create a server using the selected type
Older tomcat versions are available, though.
I guess I have to recreate some configuration setting. The question is which one? This seems to be some odd error as creating a new dynamic web project lets me configure tomcat for both of them
I had a similar problem, but my solution is a little simpler. The problem was causesd by renaming the original folder that was referenced by the server definition.
Go to Window/Preferences/Server/Runtime Environments, remove the broken reference. Then, click 'Add' to create a new reference, select the appropriate tomcat version, click next and you'll see the incorrect path reference. Fix it. Move on.