To Akr: (somehow I missed the quote button. Doh)
It seems you have a problem with the d3 starter.
Things you can do:
1) Download d3starter last version from here:
http://www.thebuddyforum.com/demonb...3-starter-start-multiple-d3s-same-folder.html .First post, click download

2) overwrite d3starter.exe with this new version. d3starter.exe is located at your YAR folder, inside the Third Party folder.
3) If that doesn't help, check d3starter is working properly: launch it on a command line like this: D3Starter.exe "C:\Diablo3\Diablo III.exe" 5. "C:\Diablo3\Diablo III.exe" is the path to your diabloIII executable, change it accordingly. This should launch 5 d3 windows.
4) Note you have to execute Yar as admin, or at least set on the d3 starter to be executed as admin, to work properly.
I hope it helps; though problems could be related to your OS language being Polish (it seems) . Mine is spanish and I have some similar problems too. Guess we'll have to wait for Sinterklaas to finish up his new home stuff to get him back on track.