Due to changes in the last.fm api this script stopped working recently. I fixed it, but did not really test it, so please contact me if something's wrong.
However, I did not fix the java version. It is unfinished, anyway, and I don't have the time to continue the work now.
Blank page after hitting the submit button? In that case you have more musical data than the script can handle. Try a shorter period or wait for an offline version. (But you would wait pretty long, I guess...)
Incorrect artistcounts? See here, maybe i'll get behind this problem if there are more cases for that I can investigate.
Give us a listen: Caldron - Metal from Witten, Germany