This morning, I cloned a completely updated and patched Ubuntu 10.04 x64 server for the purpose of updating to 12.04.

The 12.04 update seemed to go fine, but after the reboot, the first
Code:
# apt-get update
# apt-get dist-upgrade
failed with this output:
Code:
# apt-get dist-upgrade
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
3 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue [Y/n]? Y
Setting up libxml-sax-perl (0.99+dfsg-1ubuntu0.1) ...
update-perl-sax-parsers: Registering Perl SAX parser XML::SAX::PurePerl with priority 10...
Can't locate XML/NamespaceSupport.pm in @INC (@INC contains: /etc/perl /usr/local/lib/perl/5.14.2 /usr/local/share/perl/5.14.2 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/5.14 /usr/share/perl/5.14 /usr/local/lib/site_perl .) at /usr/share/perl5/XML/SAX/PurePerl.pm line 20.
BEGIN failed--compilation aborted at /usr/share/perl5/XML/SAX/PurePerl.pm line 20.
Compilation failed in require at /usr/share/perl5/XML/SAX.pm line 153.
dpkg: error processing libxml-sax-perl (--configure):
 subprocess installed post-installation script returned error exit status 2
dpkg: dependency problems prevent configuration of libxml-libxml-perl:
 libxml-libxml-perl depends on libxml-sax-perl; however:
  Package libxml-sax-perl is not configured yet.
dpkg: error processing libxml-libxml-perl (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of libxml-sax-expat-perl:
 libxml-sax-expat-perl depends on libxml-sax-perl (>= 0.03); however:
  Package libxml-sax-perl is not configured yet.
dpkg: error processing libxml-sax-expat-perl (--configure):
 dependency problems - leaving unconfigured
No apport report written because the error message indicates its a followup error from a previous failure.
                          No apport report written because the error message indicates its a followup error from a previous failure.
                                                    Errors were encountered while processing:
 libxml-sax-perl
 libxml-libxml-perl
 libxml-sax-expat-perl
E: Sub-process /usr/bin/dpkg returned an error code (1)
Attempts to use
Code:
# apt-get install -f
to correct the problem has failed.
A little searching suggested that the missing dependency should be corrected by
Code:
# apt-get -f install libxml-namespacesupport-perl
That returned:
Code:
libxml-namespacesupport-perl is already the newest version.
3 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue [Y/n]?
Which fails in exactly the same way as shown above.

Found this post http://ubuntuforums.org/showthread.php?t=1457166 which seems similar, but the fix didn't work. No language issues on the machine. The locale seems to be set and correct.

https://bugs.launchpad.net/ubuntu/+s...rl/+bug/366969 has what seems like the same issue from 2009.

Is there a more useful dpkg log with details somewhere? /var/log/dpkg.log isn't very useful.
Code:
2012-10-07 13:19:05 startup packages configure
2012-10-07 13:19:05 configure libxml-sax-perl 0.99+dfsg-1ubuntu0.1 <none>
2012-10-07 13:19:05 status half-configured libxml-sax-perl 0.99+dfsg-1ubuntu0.1
Ideas to correct this dpkg error/issue?