(Eclipse 3.4, Ganymede)

I have an existing Dynamic Web Application project in Eclipse. When I created the project, I specified 'Default configuration for Apache Tomcat v6' under the 'Configuration' drop down.

It's a month or 2 down the line, and I would now like to change the configuration to Tomcat 'v5.5'. (This will be the version of Tomcat on the production server.)

I have tried the following steps (without success):

• I selected Targeted Runtimes under the Project Properties
  The Tomcat v5.5 option was disabled and The UI displayed this message:
  If the runtime you want to select is not displayed or is disabled you may need to uninstall one or more of the currently installed project facets.
• I then clicked on the Uninstall Facets... link.
  Under the Runtimes tab, only Tomcat 6 displayed.
  For Dynamic Web Module, I selected version 2.4 in place of 2.5.
  Under the Runtimes tab, Tomcat 5.5 now displayed.
  However, the UI now displayed this message:
  Cannot change version of project facet Dynamic Web Module to 2.4.
  The Finish button was disabled - so I reached a dead-end.

I CAN successfully create a NEW Project with a Tomcat v5.5 configuration. For some reason, though, it will not let me downgrade' an existing Project.

As a work-around, I created a new Project and copied the source files from the old Project. Nonetheless, the work-around was fairly painful and somewhat clumsy.

Can anyone explain how I can 'downgrade' the Project configuration from 'Tomcat 6' to 'Tomcat 5'? Or perhaps shed some light on why this happened?

Thanks
Pete