Unable to add new files after checking out a tag

[b_dompe]

We bring a new tree up to date with the latest 'stamped' release by 
using "cvs update -r<releasename>", where the release was created 
with "cvs tag -RF <releasename>".

This seems to work for existing files.  However, when people try to 
add a new file to the repository, they get the error "cannot add file 
on non-branch tag <releasename>".  

We've only ben able to fix it by erasing the tree and doing a cvs co. 
That gets the latest revision of every file though, which is not what 
we want. Is there a way to fix this?