Just upgraded OTRS to the latest version 3.0.6 by following the UPGRADE steps. Although I followed the instructions to 100%, Apache didn't start after the upgrade was done.

The following Apache error log entry indicates where the problem can be found:

[Thu Apr 14 08:58:26 2011] [error] Can't locate Crypt/PasswdMD5.pm in @INC (@INC contains: /usr/Custom /usr/Kernel/cpan-lib /usr /opt/otrs/Custom /opt/otrs/Kernel/cpan-lib /opt/otrs/ /etc/perl /usr/local/lib/perl/5.10.0 /usr/local/share/perl/5.10.0 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/5.10 /usr/share/perl/5.10 /usr/local/lib/site_perl . /etc/apache2) at Kernel/System/User.pm line 17.\nBEGIN failed--compilation aborted at Kernel/System/User.pm line 17.\nCompilation failed in require at Kernel/System/Web/InterfaceAgent.pm line 30.\nBEGIN failed--compilation aborted at Kernel/System/Web/InterfaceAgent.pm line 30.\nCompilation failed in require at /var/www/otrs/scripts/apache2-perl-startup.pl line 68.\nBEGIN failed--compilation aborted at /var/www/otrs/scripts/apache2-perl-startup.pl line 68.\nCompilation failed in require at (eval 2) line 1.\n

[Thu Apr 14 08:58:26 2011] [error] Can't load Perl file: /var/www/otrs/scripts/apache2-perl-startup.pl for server otrs.localhost.local:0, exiting...

We can clearly see, that the problem comes from /var/www/otrs/scripts/apache2-perl-startup.pl. Actually, you have to adjust the OTRS installation path in this file as well, if you haven't installed OTRS in /opt/otrs:

# set otrs lib path!
use lib "/opt/otrs/";
use lib "/opt/otrs/Kernel/cpan-lib";
use lib "/opt/otrs/Custom";

These paths need to be adjusted to your actual OTRS path. Unfortunately this is not mentioned in the UPGRADE guide but it isn't difficult to solve the problem.