Been loving this game (Lv 48, wood elf, stormcloak) but have now discovered that a strange quirk that happened as I was completing the Civil War questline is ruining some of it.
Basically, when I started the final Battle of Solitude I was arrested by a guard for past crimes and zoomed inside the castle, bypassing all the fighting. However the quest continued and I got to defeat the imperial leader and see Ulfric named king at the kingsmoot etc - and got the achievement - so thought all was well.
Until...ages after I started the Dark Brotherhood quests and found I couldn't get in to Solitude when required because it literally wasn't on the map.
Appears the game still thinks I haven't completed the Battle for Solitude as Ulfric & co are now back outside the city's gates, and no matter what I do I can't trigger the battle - so far it's stopping me continuing with both Dark Brotherhood and Bard's College questlines.
Has anyone there found a solution/workaround to this, or am I looking at a demoralising 'load earlier save'?

It sounds like you're going to have to reload a previous save. According to wikia, if you have a bounty when entering Solitude, it will take you outside of Castle Dour, and you're supposed to go back to the main gates to meet Ulfric and everyone else instead of going on without them.

Does anything happen if you approach Ulfric and try talking to him?

Nope, other than him spouting something about killing Imperials. When I try to get back into the city the game just keeps telling me that I need to 'help the stormcloaks defend Solitude'. Very annoying. (I can actually get back in by pickpocketing and getting deliberately caught, but things are seriously out of whack inside).
Think I'm just going to have to finish everything else I can (I'm level 49 and have notched up just about all the achievements) and then load an old save with the single intention of finishing the Dark Brotherhood storyline.
Annoying, but it's a plan!