Admin login not working
 

I did a complete, new install on my board and all went fine, until trying to log into the Admin/CP. It accepts my username and password, thanks me for logging in and promptly directs me right back to the login screen for the Admin/CP?? On my first install this didn't not happen. Any ideas what I did wrong on the clean install? yes, I set up my admin user account. Also, I just logged out and it won't allow me to log back in, although my account is listed as the adminstrator.