calibre-parallel crashed with ValueError in lxml.etree._utf8 (src/lxml/lxml.etree.c:22060)(): All strings must be XML compatible: Unicode or ASCII, no NULL bytes or control characters

Was trying to convert an html file to an epub

ProblemType: Crash
DistroRelease: Ubuntu 12.04
Package: calibre 0.8.38+dfsg-1
ProcVersionSignature: Ubuntu 3.2.0-20.33-generic-pae 3.2.12
Uname: Linux 3.2.0-20-generic-pae i686
ApportVersion: 1.95-0ubuntu1
Architecture: i386
Date: Sat Mar 31 12:42:57 2012
ExecutablePath: /usr/bin/calibre-parallel
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Alpha i386 (20120104)
InterpreterPath: /usr/bin/python2.7
PackageArchitecture: all
ProcCmdline: /usr/bin/python2.7 /usr/bin/calibre-parallel
PythonArgs: ['/usr/bin/calibre-parallel']
SourcePackage: calibre
Title: calibre-parallel crashed with ValueError in lxml.etree._utf8 (src/lxml/lxml.etree.c:22060)(): All strings must be XML compatible: Unicode or ASCII, no NULL bytes or control characters
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo