Need help with Admin login

[Winniemae]

Please help with Admin login. I have never had an issue with logging in to my builder control panel but today I get the message-[u]You are successfully logged in [/u]THEN another message pops up saying You are not logged in- wait a moment.... THEN back to the login screen. This cycles over and over. Input please! Thank you

[LiroyvH]

I'm having the vague idea you're not talking about a SMF powered forum but about something else?