Got a headache by trying to use the flash version of Prefuse, which is called Flare, in the Flex2 builder environment (which I found out, you can get for free if you're a student). Basically the tutorial works fine till you reach the most interesting point: adding the Flare libraries into the project.

The library import facility doesnt seem to work: I get funny errors related to the eclipse editor that doesnt even let me visualize the file contents of the imported libraries:

Unable to create this part due to an internal error. Reason for the failure: Editor could not be initialized.

java.lang.NullPointerException ....bla, bla bla....

So, after some googling I found out that somebody else had the same problem:

There's a pretty good tutorial that I, as a beginner, found straightforward. I ran into some problems when I was trying to "import a library into another project," but per Jeffrey's suggestion, I upgraded to Adobe Flex 3 beta (currently a free download). That cured my problems. Adobe Flex is apparently still a little rough around the edges. Oh right, and the tutorial provides instructions on how to develop with Flare in the Flex Builder environment.

Mind that the Jeffrey he's talking about is the creator of Flare. Flex 3 is the solution...
So, word of advice: if you want Flex for the Flare capabilities, don't go through release 2!!!