cannot login after I setup Domain mapping plugin

I setup the domain mapping plugin as per the instructions on this page
https://premium.wpmudev.org/project/domain-mapping/?ht2=1&utm_expid=3606929-52.ZpfeUjXqSWOCaoohIqoFQQ.1#product-usage
After that, when I logout and try to log back in, I am not able to get in. It keeps showing me the login screen though I enter the correct user/paswd.
The only way was for me to log back in was to comment out
define('SUNRISE', 'on');

Right now, I have it uncommented, so I am unable to log back in.
Please help.
Sri