Can you login as any user? If not it is likely to be a setting in your web.config file.
Make sure you have transferred across the correct settings in the web.config file for:
Installation Date + Machine Keys, ie:
Within the
< appSettings> You also need to add the installation date:
< add key="InstallationDate" value="6/30/2005" />
< /appSettings>
and you also need to copy across the validation key and description key within the
< machineKey tab
< machineKey
validationKey="20DAE7795171D2ACA41CC59A5FA162CEC17AK1B2"
decryptionKey="01CC59541FD47BF534F7G126B14F618CD4B8771D0A1EECLP"
decryption="3DES"
validation="SHA1"/>