I know this is an older thread - but I had problems w/ a fictionwise title - Children of Dune - the convertlit couldn't downconvert the file - received an error from the command line, unbalanced html extra ending and when I used the first gui, when I looked at the exploded files, they were empty - I used the ConvertLit gui from here:
http://dukelupus.pri.ee/convertlit.php and the file was down converted properly, and I could then successfully use Calibre to convert the .lit file to the format I needed.
Goof that I am - I reread this thread - and running just the program w/ the old file name and the new does remove the drm and Calibre works fine w/ that.
But, the GUI at the site I gave above does have a nice interface - you can easily select lots of books to de-DRM.