Bluesmike:

Try it by running your Zip application and starting the process from the application (Open file...) and then pointing it at the target file.

It is an error caused by some weird data in the file that maps applications to kinds of files. These mappings are sometimes stored in the preferences for the browser itself, and sometimes in the system files, and tell the computer which kind of application to use according to the file type. Yours has gotten crossded up into thinking Acrobat is the very thing to open Zip files with.

A