For all of you that tried all possible soloutions and had no luck, try this one:
Create .htaccess file in your blog directory with this data:
<Files xmlrpc.php>
SecFilterInheritance Off
</Files>
Some guy posted this at
https://www.ads-software.com/support/topic/83948?replies=5
and it worked for me and I tried all possible solutions before that (switching to IE, using domain/subdomain/ip for my adress, changing permissions of xmlrpc.php etc etc)