Aditya,
Before you go spouting off about RTFM, please re-read my post. If you download the "latest" version of moodle from the link I posted above and extract it to an empty folder you will see that the version.php file is incorrect.
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
I agree, you shouldn't unzip over previous files normally but in my case I did it from the command line and forced it to overwrite so it wasn't the issue.
The real issue here is the In-Moodle Download Link to the latest release points to a version that had an older version.php file bundled with it.
Bad packaging on someone's part.