I've come to the conclusion I just can't seem to rate blogs I haven't rated before on this using this browser (the "basic" Mac one. Will rate them from time to time but only after switching to other browsers, Firefox etc., which I do more rarely lately.)
Update: things work rather poorly with fubar and Safari , not great with fubar and Firefox, but rather well with fubar and Google Chrome, on my computer, so I've been using Chrome as my primary browser for some time now... (Nov 2010)