How did you put this on your server?
Did you upload all of the files from your local computer or did you upload the compressed file, decompress it on your host and move it to the right directory from there?
My guess without looking at your system is that you have a problem with your files.
I am not at home at the moment to be able to suggest which files directly to move over but there is a MD5 file check that you can run. There are two files, one contains a list of all of the files and their MD5 hashes and the other is a PHP script that reads the list and compares it to the files on the system.
I believe the php script is a file called "checksum.php" and the other called "checksum.md5" these might be in the extras folder. Move these to your base folder and then run the checksum.php file and wait (Takes about 3 minutes on my local server).. It will check all of your files for you and let you know if any of them are incomplete.
You would run this file by calling http:/yoursite.com/checksum.php from your browser once you have copied the files over. (Using the correct URL for your site of course and the correct file name if it isn't checksum.php)
Each step is in a separate file and my guess is that for some reason the script is not reading the next file so it defaults back to the same file.
You could go into the install folder and check the permissions of the files as well. If the permissions are bad it will do weird things. I have found when I upload a new site I need to upload the compressed file, decompress it on the site, then move the proper files into the correct folder. If I decompress it on my local computer then ftp all of the files it takes MUCH longer and sometimes the file permissions get messed up.
Rodney