I am having the same issue with Dot5 Hosting. When I login with the incorrect username/password combination, I get the expected error. When the username and password are correct, I am redirected to the home page and I am not logged in. I ran the yii/requirements/index.php on the server and it passed other than a warning on the SOAP extension. I’m not sure what the issue is. The support has no idea what yii is, when I asked about it before I uploaded they thought it was something like Dreamweaver, a site building program not pure php code.