I am not quite sure which quest or which action might have started this, but this is what happens right now:
I enter Solitude (through the door at the foot of the cliff) and walk towards the slope leading up to the Fletcher and the Blacksmith. I can interact with the regular Solitude Guards without any problems, but as soon as I walk through the arch between the Fletcher and the Blacksmith and enter the courtyard, the "special" Solitude Guards standing in front of the big door on the left spot me and attack me. After that, all the regular Guards also attack me.
I have no bounty on me in any of the holds, and the Guards do not even give me an option to surrender.
Why do the Guards in the Solitude Courtyard attack me on sight, and how can I stop it (preferably without violence)?