Having a problem when I install WPMU logging in

I installed WPMU and once completed, it directs me to log in. When I try to log in, two issues occur. First, it displays 'password field is empty'. I enter a space and delete it to clear that but when I submit it does not let me. it just stays in a loop that does not allow me to login to my dashboard as admin. I had to revert the htaccess and wp-config file to the original to be able to login. What can be going on?