Captive portal login failure for usernames with syntax of (Firstname.lastname)

[networknut]

I setup captive portal and am having a minor issue, I got it working fine and customized the authentication page (NOT THE PROBLEM) works great except one thing. If the username is in the syntax "firstname.lastname" the login fails and i see this in the Logs

"logportalauth[64800]: Zone: captive_portal - FAILURE: firstname.lastname, 30:d6:c9:xx:xx:xx, 10.xxx.xx.xx"

however if i create another user with a username such as "test" or "bill" it works fine. Any ideas?

[cmb]

Local user auth or RADIUS?

[networknut]

Local auth for now.