Trouble checking out some drupal modules using CVS

I am trying to replicate an existing setup using CVS to check out modules this time. This has gone well for a number of modules but I have not been successful with several modules:

format_manager 6--1-0-beta2
path_redirect 6--1-0-beta1
sitemap 6--1-0

Is there something in the way I am writing the version information that could be getting in the way? Is there anything about these particular modules and CVS that might explain why I'm not seeing any files for them after trying to check them out?

Thanks for any help.