Well, I'm not very proud of it, but I got the Flattr button working somehow. I've added the static button to the theme's template, so it shows on every node.
OK, technically it's not pretty, but to be fair, my current Drupal install isn't either (that's also the reason why Drupal's Flattr module doesn't work for me in the first place).
Can't wait for Drupal 7 to come out, get myself a PlugComputer and migrate to it.
…actually can't wait until I get that done, with the state of my DB this should be quite an ugly ordeal :\
hook out → taking a nap to cure the headache, then working on a text to finish my application for that legal counselling job