Only things I can recommend is to make sure "Remember username and password" is set to Yes. This is important because the voting system checks to make sure you had made an explanation and it uses the cookie. If that is enabled and you still can't vote, try changing "Browse board with cookies" to No. That will pass the session info via the url. If its already No, try setting it to Yes and see if that works. Other then that, not much else I can recommend.

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-Kalvin