I don't think you should be locking the remote editor, restricting such a feature in mIRC is not only dangerous and silly, but considered lame by many. Scripts that have such features are rarely used.
If the reason you want to do it is "ripping" (this is assuming you are releasing some sort of script) then that is the price you pay for releasing scripts to the public. People sometimes do rip stuff - good websites usually reject these kind of scripts though.
As for the DLL not working, it probably hasn't been updated to work with 6.12/6.14 or something - contact the author of the DLL. Make sure you're using it correctly though. I'd recommend using the latest version
(6.14) of mIRC though so you can benefit from the latest bug fixes and features and scripting methods.