plugin software-center.py generates error "need more than 1 value to unpack"

When trying to start software-center or using update-apt-xapian-index it crashes with the following output:

michael@montreal:~$ sudo update-apt-xapian-index -v
Reading plugin /usr/share/apt-xapian-index/plugins/aliases.py.
Reading aliases from /usr/share/apt-xapian-index/aliases/popular-apps...
Reading plugin /usr/share/apt-xapian-index/plugins/app-install.py.
Reading plugin /usr/share/apt-xapian-index/plugins/apttags.py.
Reading plugin /usr/share/apt-xapian-index/plugins/cataloged_time.py.
Reading plugin /usr/share/apt-xapian-index/plugins/debtags.py.
Reading plugin /usr/share/apt-xapian-index/plugins/descriptions.py.
Reading plugin /usr/share/apt-xapian-index/plugins/display_name.py.
Reading plugin /usr/share/apt-xapian-index/plugins/origin.py.
Reading plugin /usr/share/apt-xapian-index/plugins/relations.py.
Reading plugin /usr/share/apt-xapian-index/plugins/sections.py.
Reading plugin /usr/share/apt-xapian-index/plugins/sizes.py.
Reading plugin /usr/share/apt-xapian-index/plugins/software-center.py.
Traceback (most recent call last):
  File "/usr/sbin/update-apt-xapian-index", line 101, in <module>
    if not indexer.setupIndexing(force=opts.force, system=opts.pkgfile is None):
  File "/usr/lib/python2.7/dist-packages/axi/indexer.py", line 466, in setupIndexing
    self.plugins = Plugins(progress=self.progress, system=system)
  File "/usr/lib/python2.7/dist-packages/axi/indexer.py", line 89, in __init__
    addon = Addon(fullname, **kw)
  File "/usr/lib/python2.7/dist-packages/axi/indexer.py", line 49, in __init__
    self.module = imp.load_source("axi.plugin_" + self.name, fname)
  File "/usr/share/apt-xapian-index/plugins/software-center.py", line 13, in <module>
    from softwarecenter.db.update import index_name
  File "/usr/share/software-center/softwarecenter/db/update.py", line 89, in <module>
    axi_values = parse_axi_values_file()
  File "/usr/share/software-center/softwarecenter/db/database.py", line 57, in parse_axi_values_file
    (key, value) = line.split()
ValueError: need more than 1 value to unpack

Can somebody please give some instructions on how to further identify the issue? I have seen several bug postings about this but nobody seems to be able to help.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: apt-xapian-index 0.44ubuntu5
ProcVersionSignature: Ubuntu 3.2.0-24.37-generic 3.2.14
Uname: Linux 3.2.0-24-generic x86_64
ApportVersion: 2.0.1-0ubuntu7
Architecture: amd64
Date: Sun May 6 12:35:50 2012
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: apt-xapian-index
UpgradeStatus: Upgraded to precise on 2012-05-05 (0 days ago)