I think I have this figured out!!
I had the same problem. Login, then the screen refreshes to the login page over and over again.
My book mark was the login page. I changed my book mark to the dashboard page and everything works fine now.
When you enter the url for the dashboard page, you get redirected to the login page. When you enter the correct login information, it sends you on to the dashboard page you requested.
Since I had the login screen bookmarked, (...redirect_to=http%3A%2F%2Fwww.blah blah blah), after I entered the correct login information, it sent me to the page I had bookmarked - the login screen.
After you do that once, you are logged in. If you then enter the url to your dashboard, you will go straight there. But since you are trying to log in and the screen keeps refreshing, you enter your login information again and again and again becoming more and more frustrated.
I tried clearing my cache and switching browsers etc and nothing worked. This appears to be the problem for me. I hope this helps you too!