Problems setting up a username for church page

When I was going through the administrative steps to set up our church page, Facebook offered me the option of setting up a username for the page, which I understand to be a way of putting a unique text string after [You must be registered and logged in to see this link.] that will make it easy for people to find our page. The name of our church is Unity Center Of Muskogee. The input box says I can't use spaces, so I picked the username UnityCenterOfMuskogee. But when I then click "Check availability" it keeps choking on my entry, saying the username must contain at least five characters. Well, I have 21 characters, so what's the problem?

Please try these 2 ways to change your page's username and see if you have any luck:

a) Straight from [You must be registered and logged in to see this link.], select your name from the list, type its username and confirm.

b) Go to your page, click the Edit Page button, Resources tab, Select a username. Type it and confirm.

Same result on both of them?