So I'm in the planer sphere, got the demon heart fed it to the machine got back to my world, went and found lavok and began to fight him, but he will not die. He is at near death and is not attacking or anything just standing there lettin my Beastmaster, Mazzy, and Valygar unload on him for like ever and doesnt do anything. Why cant he die, what am i Missing here. is this a lame bug that will screw up this quest so i cant finish it?

Sounds like it :)

He is supposed to deliver a dialogue when he reaches near death so STOP POUNDING ON HIM!!!

Sometimes the "just before death speech" can't trigger if you keep pounding the enemy. Dace's advice should fix it. Otherwise - are you patched and do you have the Baldurdash Fixpack installed?

I have no patch's installed, but I have tried just standing there and nothing happens 'cept me gettin peaved at that A-hole.

Getting the official patches is essential to a bug-free game, IMO. I haven't had a trouble yet with quest or game ending bugs since installing the official patches and the Baldurdash Fixpack. I think that the problem you describe is fixed in the official patch.

Yep, Lavok not talking is specifically mentioned in either the official patch (link to bioware from the link in my sig), or from Baldurdash (also linked from my page).

This very common bug can occur as a result of fake-talk, as well as from killing the guy all too fast.
BioWare patch and Baldurdash Fixpack will solve this problem.

Yeah i DL the patch and it worked, so be to ye.

<span style="color: lightblue">He isn't meant to trigger a speach at this point. The demon heart has already been found - meaning, Lavok has already said his "What is this? The force that possessed me is... is gone" speach. Meaning, you're meant to talk to Lavok, not fight him yet.