by Howard Miller.
Neverthless, if what you say ("unzipped it over my previous version") is true, then Aditya is quite correct if, perhaps, a little insensitive.
You simply musn't do that. Due to the way that Moodle locates plugins and such this method of upgrading is not recommended and (in particular) not supported.
As an alternative you could always get your code from Git - Git_for_Administrators