Tried masking and now can’t login

Hi,
I was happily redirecting one domain to another with a subdirectory (eg. mydomain.com to second.domain.com), when I read about masking. I followed the instructions from my web host, but my blog became a white page with text and links, no theme. I also couldn’t log in to get to the admin side to try to fix it. I went back and reversed the process, which got me my blog back, but I still can’t login to work on it. I’m not getting any errors, just that I write my user name and password and click login and nothing happens.
Does anybody have any suggestions on how to fix this?