Copy columns using JS

Hi,
I am working on a script to copy some of the columns into another form like a clone process. I am using window.Open("main.aspx?etn=incident&pagetype=entityrecord&extraqs="+encodeURIComponent(extraqs),"_blank",features,false)
to open new window with all the copied data in it. It works fine until I added a new column to the script and it fails saying "404 - File or directory not found". I checked my url and tried seperately with the newly added column and it works that way.
But when I append that new column to my existing column it fails. Some one please guide me how to troubleshoot this issue? I did try one by one column in the url and it works absolutely fine but fails with the newly added column.
Thanks for any help.