Was wandering back to town in the wilderness and ran into a Vampire and his thrall.

Funny thind is they let me walk right up to them and even had an option to talk to them. They wouldn't really say much tho....just a quick "how can i help you?" or something and then the dialog box would go away. They didn't attack at all.

After a reload, they were back to normal Vamp behavior and attacked on sight....

Anyone else seen this glitch?

Not with vampires but I've had similar behaviors from Forsworn. They sometimes spout the random one liners any normal npc will say and just occasionally act odd.

It seems most human enemy npcs are the same as friendly ones programming wise. They are just set aggressive, which means a little glitch can easily prevent them from behaving aggressive. Which results in stuff like this.