Branching failed in eclipse 3.1.1

[James Lee]

I got this message when branching in eclipse 3.1.1:

cvs tag "/myproject/Root_branch-test" "/myproject"
    cvs tag: nothing known about Asmera
    cvs tag: nothing known about Timbuktu
    cvs tag: nothing known about Buenos_Aires
    cvs tag: nothing known about Catamarca
    cvs tag: nothing known about Cordoba
    cvs tag: nothing known about Indianapolis
    cvs tag: nothing known about Jujuy
    cvs tag: nothing known about Louisville
    cvs tag: nothing known about Mendoza
    cvs tag: nothing known about Faeroe
    cvs tag: nothing known about Belfast
    cvs tag: nothing known about Yap
    cvs [tag aborted]: correct the above errors first!
    The server reported an error while performing the "cvs tag

The steps I took are these:

1. Right click on project node in Package Explorer and then click Team -> Branching...;
2. Type branch-test as the branch name, keep the defaul version name and then click OK.

It didn't give any other clues. What's wrong with the branching?

Thanks.