Access denied when logging in

The problem I experienced:
-I encountered this problem when I copied a live drupal site to my local machine for testing.
-All files and folders are a exact copy of the live site.
-I exported the database, and imported it on my local server.
-I made the necessary changes to let drupal make connection to the database on the "new" server.
-All pages work in the same way as on the drupal site. So the connection to the database works.
-When I log in I don't get to the userpage as usual. Instead I get the "Access Denied" page.
-The same happens for all users.
-If I type the wrong password I get a "wrong usernamn or password" message.

When I did this I followed the instructions here, http://drupal.org/node/75545.

I wouldn't be surprised if there already is a post or issue with a solution for this problem. But after spending +5 hours searching and reading about all kinds of solutions and fixes to similar problems I still have the same problem.

This is the closest i came, http://drupal.org/node/20397#comment-1015681 (probably the most commented post ever). I tried most of the suggested solutions here, ie. clearing cache, clearing cookies, add settings about cookies in settings.php, fixing problems directly in the data base. But nothing helps.

I think this is quite serious since it affects all users, including USER-1!

Previous system (live site):
Linux, PHP 4, Mysql 4.1.2
Path: http://bagjakt.org/

Current system (local test):
Windows XP, XAMPP 1.6.6, PHP 5, Mysql 5.0.51
Path: http://localhost/bagjakt/

Modules:
+ CCK
+ Views
+ Taxonomy Menu
+ Admintration Menu
+ FCKeditor
+ more modules

Thankful for a solution!