Every throne room i visited from the start is locked. I've never commited any evil acts, guards in castle Gryphonheart and Navan are friendly, but throne rooms are locked. Is there anything to do first, then you get access to throne rooms?

What is your current main line quest?

Early in the main story line the major throne rooms are locked. Flavor-wise, you simply aren't important enough to rate a meeting with the monarch in Erathia or in Tularean Forest.

Ah, thats cool, I got a bit worried. Yes, I didn't do anything besides clearing Harmondale Castle, visiting and clearing Barrow Downs, Erathia and Tularean Forest including all sites (except "friendly" ones). But I hadn't done anything with the castle and the seer said something about gaining fame, but I thought you go to lords for that.

Then yes, for now the throne rooms in Erathia and Tularean Forest are supposed to be locked. You'll have ambassadors in your castle to indicate when the monarchs are willing to meet with you, and the throne room doors will be unlocked in the same time frame. These events (ambassadors appearing and doors being unlocked) are independent, but both are triggered by completion of the same main story quest.

You get fame by completing quests, but the fame to which the Seer is referring is more like recognition as the new Lords of Harmondale. If you've been talking to pretty much anyone, then you'll have noticed that no one expects you to remain the Lords of Harmondale for long (the position has basically been a revolving door for decades).

Gameplay oriented warning: Do the side quests you want to do before you complete the Dwarf king's quest. The next several main-story quests are timed, and can be missed. After you've turned in the quest, go back to your castle in Harmondale and you'll find out what you need to do next.

I can be more specific if you like, but I'm trying to be vague until I know how much detail you want.

If you haven't talked to the Butler in the tavern and actually completed the quest to clear out Castle Harmondale, then that's what you have to do next.

Otherwise, the throne room that you need to visit next will be locked too.

SPOILERS

When you complete the quest to clear out Castle Harmondale, the throne room in Stone City will open to you.

When you complete the quest that you get in the throne room of Stone City, the throne rooms in Castles Harmondale, Gryphonheart, and Navan will open to you.

There are other areas that will remain closed to you, but you'll find out more about them in due time.