There is a bug in WP-PostRatings 1.11 together with WordPress 2.1.x which will not remember any ratings if you have rated the post. The bug seems to go away if you are using WordPress 2.2. I presumed there is some changes to the add_post_meta() and update_post_meta() in WP 2.2. I have since fixed the bug and now it works perfectly on WP 2.1.x and WP 2.2.
If you guys have previously downloaded WP-PostRatings 1.11, kindly re-download it again. Sorry for any inconvenience caused.