Symptom
You enter a Rendezvous name that includes a period in the Sharing preference pane. When you subsequently go to a different preference pane and then return to the Sharing pane, you discover the Rendezvous name was not saved.
Solution
Do not use a period in your Rendezvous name. To learn about creating a valid Rendezvous name, see technical document 106964, "
Mac OS X 10.2: About Your Computer's Rendezvous Name".