Redmine

Hi
I'm trying to set up redmine to control access to the svn users using active directory. The error in the "/var/log/httpd/redmine_error_log" is:

Can not call method "prepare" on an undefined value at /usr/local/lib64/perl5/Apache/Redmine.pm line 360. \ n
Can not call method "prepare" on an undefined value at /usr/local/lib64/perl5/Apache/Redmine.pm line 468. \ n

The lines in Redmine.pm file shown in the log are:

[line 360] my $sth = $dbh->prepare("SELECT value FROM settings where settings.name = 'login_required';");
[line 468] my $sth = $dbh->prepare($query);

I made several searches on google but could not resolve this error, anyone know what can it be?