if you used all the same stuff as above. and had no spawns just like above. and added the AC column with no errors. Then yes you need to set the Null values to 0.
Use this command in the sql command line
Code:
update npc_types set ac=0 where ac is null
This has worked for me, and a friend.
edit : By the way, let us know how it works.
edit: Also one more thing, I believe that this command will set the AC vallues of the mobs to 0.
But i think i may have found an alright solution. check out this post
http://www.eqemulator.net/forums/viewtopic.php?t=15381