chown incorrectly identifies account names containing periods as being invalid. You may only chown files to such users by using numeric user-id's. I discovered this problem while writing a script on the SPARC platform, but I'm hazarding a wild guess that it's not a SPARC specific problem. Here's how to duplicate it. useradd toecheese.com mkdir any_dir chown toecheese.com any_dir The chown will fail.
It's not a bug, it's POSIX compliance. You're not supposed to use a . in usernames. chown toecheese.com blah is equivalent to chown toecheese file chgrp com file If you absolutely need to use a . in usernames, you can work around this by using the User ID instead of the name, for example chown `id toecheese.com` file
Sorry, `id -u toecheese.com` of course.