There are ways around it! Do not panic my friend!
Firstly - instead of typing www.yoursite.com/wp-admin type: "www.yoursite.com/wp-admin.php" with the .php extension on the back - it won't refresh and you will be able to log in!
Secondly, the major problem and it its solution lies in the settings of your site! Here is how to fix it:
1. Log-in in your WordPress CMS site with the method described above
2. Go to >> Settings >> General and check whether your
WordPress Address (URL)
Site Address (URL)
...are different. If they are - this is causing your problem!
Change the URL name to be exact the same in the both cases - WordPress Address (URL) and Site Address (URL). Save the changes, go to www.yoursite.com/wp-admin, fill in your information and you are ready to go! :-)