If you have two sheets in one drawing and want to copy parts list from sheet1 to sheet2, NX will give you a message, that you have to set appropriate variable. Here is what you have to do:
1. go in the C:\Program Files\Siemens\NX 8.5\UGII fodler
2. find and open the file ugii_env_ug.dat
3. search for the variable UGII_UPDATE_ALL_ID_SYMBOLS_WITH_PLIST
4. change the value of the variable from 1 to 0 (UGII_UPDATE_ALL_ID_SYMBOLS_WITH_PLIST=0)
5. save the file
Now, open NX again and you will be able to copy/paste the parts list from one sheet to another in this drawing. I tried this in NX8.5 and it works.
REgards.