In Neverwinter Nights 2 the sneak attack ability is incorrectly implemented when it comes to flanking. It only works when you're behind the target but not when it is facing you, regardless of any allies flanking it.
You are supposed to (as per D&D 3.5 rules) get sneak attack so long as you and and ally are flanking it, not matter the creature's facing.

Was there ever any kind of fix for this? A mod or any such?
(I just loaded up a storm of zehir save to test this, two people, one is a rogue. flank first monster i find (ogre). As soon as it faces the rogue, no more sneak attacks.)

Is this "incorrect", or is NWN2 using the "Combat Facing" variant rule, correctly?

In that case you should be able to get a sneak attack when attacking from the rear, even if no allies are threatening.

I've never tested this, I just raise the possibility.

It is possible. Seems odd that they'd say they're using 3.5 rules but pull out some variant rule I don't remember seeing in the phb.

Did some digging. According to the manual: "<some options> OR has its back to you AND is in combat against another opponent, ..."
So it doesn't seem to follow this variant rule you mention because of the being in combat bit, nor does it follow traditional 3.5 since all you need there is to be flanking the creature (among other possibilities).

So it seems to be some weird house rule that Obsidian made up for the game.

I don't know how to test this in game, short of some kind console code that kills enemy AI since I don't recall ever getting into melee range while not being in stealth and not having the enemy turn to face me. I don't even know if there is an AI off code. Maybe I could attack a random friendly NPC.

Sorry, I was working a bit from memory. But the Combat Facing variant I was thinking of was for 3, not 3.5 (as it was found in Unearthed Arcana) - and it didn't require the foe to be in combat with another opponent. Of course, in practice it's challenging to get behind someone that isn't busy with someone else... but still, it wasn't a requirement for the sneak attack.
http://www.d20srd.org/srd/variant/adventuring/combatFacing.htm#sneakAttacks

As you say, it does "seem odd...". And I see the nwn2 wiki does believe that sneak attack is implemented normally, with flanking giving SA regardless of facing. I'm surprised nobody's mentioned this before - oh, there's a mention on the Steam forums, but it's no more helpful than I am. :)

Well, between my searching, your evident searching, and anyone else who read this but didn't reply, I'm going to say there is no player made "fix" and file this under "Oh well, deal with it."

Thanks for the input though.