fanfiction.net has made more changes again to break a couple different things in FFDL.
Attached is a version that fixes all the problems I've found. So far. I'd like to give it another day before I push another release.
Please report any further problems.
UPDATE Mar 28, 2013 - Remove obsolete beta versions
ff.net hasn't changed for hours now.
So I've pushed these changes out as a new release. If calibre doesn't report that there's a new version (1.7.19), tell it to install again anyway.