I have no idea why. I fast travel there and they attack me, all of them. They didn't seem to have any problem with me the last time I was there. Im certain I dont have a bounty... What do I do?

Try hitting one of them, then sheathe your weapon right after. That will give you a bounty and the guards will try to arrest you.

Maybe it's a glitch. Leave Solstheim and then try to do something else (trading in riverwood for example), then travel back and see what happens. !!!

I tried it, changed nothing. Tried leaving too, that didn't work. So I turned off all the AI and found out things that just make it more confusing. Its not the entire town, its that one loanshark Orc, his bodyguard, and all the guards in town (including the named one.) Not only are they automatically hostile, they are all Essential, including the guards. Or at least, they responded to the "Kill" command as if they were essential. If i actaully go and disable all these people, no one else turns hostile. If I don't disable them, the entire town turns hostile.

I tried to use the console to forceav aggression, but the game says i cant do that using scripts or the console.

What happens with previous saves? ARe you using any mods?

Anyway, try to punch on the face a NPC (not a guard!), so attacking somebody who isn't already hostile to you - which will give you a bounty. Then surrender and pay the bounty as usual.

What happens...???

do you have Dawnguard installed?

and if not, are you a vampire?

I guess they finally got tired of outlanders...

Okay, well the issue is essentially resolved. Though not in a great way. But so its clear: I use the unofficial patch mod, and that's it. Wasnt a vampire. Punching the guards did nothing since they were already hostile. I reset the AI on him and punched him, got a bounty, went to jail and payed it off, and then everyone was still hostile.

As far as I can tell, it was that loanshark orc. This all started the first time I went back to town after getting Neloth his new apprentice, when the orc shouldv'e accosted me for the 1000 gold.

I re-enabled the guard captain, and he's not hostile anymore. I re-enabled the Orc too, and he actually tries to get me to pay now... But becase he was nearly dead in essential mode when i disabled him but was no longer in essential mode, he died immediatly after starting conversation with me, both beginning and ending the quest to repay the debt.

So the issue does seem to be resolved. In a way. I still have no idea what happened though.

more probably a games glitch...