Most likely your browser are blocking the piano forum cookies. Try to set the privacy setting in your browser one or two steps lower and let me know if this makes any difference.In IE Explorer you find the settings at: Tools>Internet options>Privacy
You are aware that in your "log-in"-screen there is a box where you can activate "always stay logged in"? And there is also a timer, saying like: time to stay logged in: ... minutes. Either activate staying logged in, or increase the time till log-out.