Try uninstalling PKUNZIP and see whether this solves any of your saving issues.
Also download a regclean program (
Regclean) this should help with deleting any corrupt registry entries.
I'm also having a lot of trouble extracting zip files, getting a lot of "error in ZIP structure"
This could be due to corrupt .zip files, if you are getting them from places like Shareaza then that could be the reason.
Alternatively you could set the .ZIP file association back to its default program, do this by opening windows explorer.
Then go to TOOLS -- FOLDER OPTIONS ---- FILE TYPES
Browse for .zip? then under "Detials for zip extension" click on change and choose "Compressed (zipped) Folders"