When users try to login, they get the following message, which has never happened before:

Software error:
Can't locate loadable object for module MD5 in @INC (@INC contains: .. /home/mailscot/mailscot-www/cgi-bin/webmail/admin . /usr/lib/perl5/5.6.0/i686-linux /usr/lib/perl5/5.6.0 /usr/lib/perl5/site_perl/5.6.0/i686-linux /usr/lib/perl5/site_perl/5.6.0 /usr/lib/perl5/site_perl) at /home/mailscot/mailscot-www/cgi-bin/webmail/admin/Webmail.pm line 294

Can you help please?