Every time I try to join the Dawnguard, I'm getting attacked by everyone. I read on the UESP that one of the bugs involves being attacked by the Dawnguard if you have lycanthropy, but I don't. I'm neither a werewolf nor a vampire, but they all attack me anyway. Is there something else I might have done wrong?

If you have a bounty in any hold dawnguard will also attack.

There is also a hidden bounty bug where you won't know you have a bounty, and won't be able to go to jail.

Dunno how to get around that one actually.

Lol that was it! I didn't even know I had a bounty, but I must've had it for quite awhile. Thanks.

No problem

a bounty will do it

they could care less your a werewolf... though I have been attacked by Stendarr vigilents while in wolf form.