My character is a lvl 35 vampire, (stage 3 at this point), with lvl 84 sneak skill and 6 of the associated perks.

How, then, do low-level bandits manage to 'see' me at night when sneaking, at a great distance, even through walls sometimes?? Are they psychic, or is there some bug/ game mechanic that makes npc's hyper-aware of vampires in the vicinity, even when they are not moving or doing anything? The cross-hair does not even change when they start looking for me, nor do I get to see their positions, so in effect they see me before I even know they are there which is just WRONG.

I'm sure this didn't happen before, and it is making feeding pretty impossible... surely a glitch?

I think some might be triggered to know your there.

I was trying to sneak kill some bandits at a camp I was sent to for a bounty. I was sneaking and got spotted every time by bandits and was warned to "Go away." And yeah they still saw me crouched behind a wall.

Are you wearing heavy armor boots? Try soft shoes or leather boots.

Some Bandits go to level 28, but most of their perks are attack perks, not sneak perks.

If that's so it has never happened to me before, in 3 1/2 years of playing! I've been sneak-killing these same bandits - in daytime - at lower levels, so I don't get it.

Edit: Nope, I'm wearing light armour - and in any case I have the 'reduced armor noise' perk, whatever it is called, so it's not that. Besides, they detect me when I'm not moving.

How did you play this game a year and 4 months before release? You live in the basemant of BGS?

Did you recently add any mods to the game? And this would include mods that should not affect Sneak or detection.