When I set up the project, I connected to CVS via the CVS explorer and setup the branch I needed to access. I then right-clicked on the branch and selected “Check out as…” to create a new project with all of the code in the CVS branch. The project which was created was not a “web” project. This appears to be the critical piece.
Today, I created a web project, then went through the process again, this time specifying that I wanted to check the CVS branch out to an existing project, rather than a new one, and selected my web project.
I can now open up the JSP file without a problem.
So, in summary, the problem appears to be that I had a standard Java project, not a “web” project.
Thanks for your help.