Modifying main houses with creation kit

[skyrim76]

Hi, I'm doing ok so far with creation kit but I've encountered a problem.

 

When I add some items, furniture or Npc's in the house its fine, also when I add a basement to the house, for example, its all normal while I'm in the house, everything its like I moded but when I try to go outside game crashes. I can go inside but not able to go outside.

 

Here is what I did, I've opened original cell of the house, duplicated parts that I want to change, some parts I've cut, and attach it to the main house.

 

What I'm doing wrong?

 

Here is what that looks like.

 

 

http://i39.tinypic.com/5bnt5f.jpg

Edited February 21, 2012 by skyrim76