What have happend to the thief in newerwinter nights ??
Can I play a thief with backstabbing like in baldursgate II ..
or is the thief not included in newerwinter ??

When I read about the classes I didnt see the thief ....

you select ROGUE class levels for that. Backstab works differently. It's not a multiplier, it just adds dice to your damage. However, you can do this from rear flanking/rear positions as well as foes you catch flat-footed

The new one is better for game type settings I think. Sneak attack allows for more use and can be used in an active fight. Also if you find the "Wrist Sheath" weapon you can sneak attack in plain site durring a fight!

is there a cap on added damage?

Per the NWN Rule book it's +1d6 for every two levels. At higher level that's a fistful of dice.

That's exactly what the damage is. A 20th level thief adds 10D6 to his weapon damage for a sneak attack. However, this damage does not get multiplied in any way (critical hits, etc.); it just tacks on the end of whatever damage you normally do. Still much better, since you can sneak attack even with ranged weapons, as long as you are on flank or rear, or opponent is flat-footed. I have Tomi using his bow, and I always make sure to turn my opponent around to have his side or back to him. He usually doesn't last much longer after that. :D

I got the game last day and I've not installed it yet. Today I think if I'll get my new computer running ..=)
But I cant find in the manual that says anything about sneak attack..
how does it work, do I have to press a special button to do a sneak attack, do I need to stand i a specific position .. like in Baldursgate when you where backstabbing .. Can a thief be better at sneak attacks then other thiefs ...

im not a big fan of this games thief. backstab is ok but all his other major attributes(like traps and so fourth) are readily available to everybody. so why choose a char that can excercise such a limited ability? a mage for instance has a big cut in HP just because hes a ranged fighter with massive casting ability. thats a downfall to a mage is hit points, but makes up in spellpower. a thief loses some of his strength and hp just to gain thief abilities but now anyone can use them.so why choose a thief when you can choose a mage with thief abilities. or better yet a fighter or barbarian with thief abilities, at least that way youll have double hit points. i got a barb with excellent thieving abilities with 318 HP and deals standard damage around 22-34 3x that on critical.

A rogue gets 8+intelligence bonus skill points to spend freely on pick locks, disarm traps etc. Everyone else gets at most 4+Int bonus which only gets you a rank per 2 points spent. Nobody else can deal +10d6 damage with a ranged attack anytime they want. Rogues also get the incredibly useful use magic device skill and the evasion feats. No need to worry about fireballs or even dragon breath with improved evasion.

Can I use the sneak attack if I fight with a catana or is it just when ju are using weapons like bows or crossbows, darts etc.

Sneak attack is available to any weapon you can use, and under the circumstances called, flatfooted, a character hasn´t been able to react to you in combat yet. Flanked. You have a opponent between yourself and a friend (or at least an enemy to your enemy) or by certain feats like quicker than the eye(in NWN wrist sheath weapon it seems, sorry but going from my two hours of gameplay and 3:ed ruleset here..)

Missile weapons shouldn´t be able to give you a sneak attack when flanking but then again it´s only a game.
If you are hidden or invisible you also get sneak attack since the enemy isn´t aware of you.

Constructs, undead and some other mean monsters are immune to sneak attack.