This Membership Forms authentication is based on a  SQL Membership Provider Store.

When trying to logging with forms based authentication consider the following:

http://technet.microsoft.com/en-us/library/cc197472(office.12).aspx

http://help.globalscape.com/help/eft6/mergedprojects/sat/Editing_the_Configuration_File.htm

http://support.microsoft.com/kb/815179