Hi Jiri,
I just tested this functionality & can confirm that it works properly for me. This error usually means exactly what it says: Invalid credentials. That can include: bad passwords, bad usernames, disabled/locked accounts.
I would suggest looking at you AD servers Event Viewer Security logs to see if there are any failures for this account that may be able to give you more information on what is going on.
If this continues to be a problem please open a support ticket to have this looked into.
Hope this helps,
-Christian