I just downloaded the latest release of Eclipse Java EE IDE for Web Developers (Version: Helios Release
Build id: 20100617-1415). I installed Subclipse and installed the Vaadin plugin as per the instructions in the book of Vaadin. When I select
New → Project → Vaadin → Vaadin Project
the New Project dialog opens. However, as soon as I begin typing the project name, the following error appears:
I tested the same thing and could experience no such problem. However it seems your Eclipse for one reason or another really wants to use version 3.0 of the “Dynamic Web Module 3.0” and at the same time tries to use Java 1.5. You should be able to overcome this by clicking the “Modify…” button besides the configuration in the “New Vaadin Project” wizard. Just select suitable versions of “Dynamic Web Module” and “Java”.