I've personally had better luck with sPCK... Here's an excerpt from another thread with an example of how to use it - It's specific to what I was doing in the other thread, but you should get the idea:
... you'll need

A utility to "send to command prompt" is quite useful too - I use

for this (Crappy Avira even alerted this as an infection - It's safe)
So, download sPCK to a folder somewhere, then copy interfaces.pck from your perfect world element folder into the sPCK folder.
***IMPORTANT*** Make a backup of interfaces.pck in case you screw something up.
Right click sPCK.exe -> Send to command prompt.
Now, to extract the .pck file...
Code:
sPCK.exe -x interfaces.pck
This will generate a folder called interfaces.pck.files
... do your edits, etc ...
Save the file and close it, then delete your interfaces.pck file (the one in your sPCK folder!!!) and run sPCK again
Code:
sPCK.exe -c interfaces.pck.files
This will repack the files into a .pck
Once that's completed, copy the interfaces.pck file back to your element folder and launch the client.