In dolphin 6.1 and higher you need to go to the permalinks option in the settings menu of the dolphin admin. Untick the 'Enable friendly profile permalinks' and you should untick the others as well and save changes. If you are using the earlier dolphin 6.0 the frindly profile permalinks option is in the Advanced Settings. When it goes to the http://(domainname)/(username) link this is hiding the real link such as http://(domainname)/profile.php?ID=2. This only works if your server supports the remapping see more of the link server side. getting a 404 error means it dos not support serverside remapping.