What role and membership provider are you using?
You probably know this, but: If you go to the login page, default /util/login.aspx without the querystring argument returnUrl (e.g. /util/login.aspx?returnUrl=/) you will stay on the login page even if you successfully authenticate. The returnUrl parameter sets the location to go to after a successful login. Usually if you go to your UI Url (e.g. /secure/UI/) you will be redirected to login.aspx with a returnUrl that points back to the UI Url or whatever resource you were trying to access.
We have deployed a new Episerver 6 R2 based website on new server at NLB ( Windows server 2008 ). The website is working fine and we are able to browse the website, but we are unable to Login to Episerver CMS . As we try to Login to Episerver CMS Login page, we are redirected back to login page. It is behaving in hayward manner, sometimes it logs out automatically and sometimes doesn't allow to login.( it redirects back to Login Page instantly). We are not able to understand the exact problem.
Any help will be greatly appreciated
Thanks & Regards