Site messed up and can't log in to wordpress anymore

Hi

I tried to move my just build site to open in a different www address.

I had wordpress istalled in a http://www.example.fi/sub site and builded the site there. Now I tried to move the site to open in http://www.example.fi.

I went to general settings and changed the site to Site address url field and pressed save. I got an error message and after that nothing worked. I cannot log in to wordpress (www.example.fi/sub/admin) and nor my site is all messed up in http://www.example.fi/sub.

I checked with FileZilla FTP that all the index.php and other files are still in http://www.example.fi/sub.

What to do. We used a lot of time for building the site and now can’t even log in to wordpress anymore?

Thanks for the help