AniDB

I found for some titles I can not cast my vote. Even for animes I have in mylist, like Spirited Away. Why?

You have most likely already voted for it, look for a line in the anime description that looks something like this:

8.59 (337 votes), your vote: 9.00 - revoke

If you need to update your vote click the "revoke" link.

you should also make sure that you're still logged in.

BYe!
EXP