Plugin Deactivated Itself – Disappeared!

I was using the plugin WP-Post-Ratings and everything was going great until I went to activate a new plugin (WP-Favorite-Posts) I got an error message saying that the WP-Post-Ratings had been deactivated.

I tried deleting the plugin from the folder and re-uploading it but WordPress wont even recognize it all at (even after changing folder name and completely deleting wp-ratings from the mysql database).

Can someone please tell me how I can get WordPress to recognize the plugin and why it suddenly just rejected it causing it to completely disappear?

I have exhausted all my ideas and could desperately use some professional assistance.

Thanks in advance!