I changed my Permalink, and now I cant log in

Hi,
I read through the Forums, and couldnt seem to find a fix. It seems a very common problem.

I set up my wordpress in a different directory to the website im working on, so the current website is still hosted while I build a better improved site with wordpress. So I added a folder Called wordpress, and I could log in to the new directory fine.

No i am happy with the site, I want to set it live, so I moved the directory up a level. It didn’t quite work, I did a bit of googling, and said all I had to do was change the permalink. So I did. This is where it went wrong, and now I cant log on at all.

So I moved the wordpress back into the original directory i put it in, and the previous site is live again.

How Can I get back to the log-on page, is it a easy fix?
And what did I do wrong with the permalinks?