There has been a problem with certain maps that have been named "badly" so that you can't vote them. The problem has now been fixed.
Normally I wouldn't write news about these kinds of things but I feel this is worth mentioning for. So if there's a map that has been named not so brilliantly and it overlaps with client/server aliases, you can still vote for it using:
/votemap arenaFor example. The feature was added by Qqshka on earlier this month to make those badly named maps voteable and it actually works nicely