[quote]After saving and exiting, the changes I made are not saved.
And I get no prompt to re-encrypt it after exiting the zip file.[/quote]
Opus does not monitor or re-compress files that you extract from zip files. It just extracts them to a temp folder and launches whatever it's told to launch on them, then deletes the temp-file later.
To modify a file inside an archive, you'll need to extract it normally, modify the copy, then copy/move that back into the archive. (Alternatively, some editors can work within archives directly. I'm not sure if Notepad++ can as I don't use it personally.)
[quote]Another thing is when I open the zip with Enter, then I get a message with header "Create new file". And in the small window it says: C:\Windows\System32\system32.txt does not exist. Create it?
Why do I get this message??[/quote]
I suspect your .zip (or Archives file type group) double-click event is messed up, the same as it was for folders (based on your other thread).