Apache error when trying to authenticate in OTRS via LDAP

[PatrickI]

Hello,

we are currently having some trouble with our OTRS LDAP authentification. We are running OTRS 3.1.7 with ITSM. Most of the time everything works fine, but sometimes (at least once a day without any regularities) the LDAP authentification just won't work. When entering username and password into the OTRS login and hitting enter, nothing happens for some time and then you will receive an internal server error message.

The only error message i have found so far is in the apache error log file. It appears on every timeout and reads:

[error] [Fri Oct 18 11:17:51 2013] -e: Can't connect to OUR-LDAP-SERVER.OUR-DOMAIN: IO::Socket::INET: connect: timeout at C:/PROGRA~2/OTRS/OTRS//Kernel/System/Auth/LDAP.pm line 168.\n

It seems like the apache service can't resolve the hostname of our domain controller. When i connec't to the server running OTRS and ping the hostname of the domain controller, the dns resolves fine.
After some time, withour doing anyhting specific, the login will work again. I am kind of lost on where the problem is. Does anyone have any idea?

Thanks in advance,
Patrick


Edit:
line 168 in the ldap.pm looks like this:

# ldap connect and bind (maybe with SearchUserDN and SearchUserPw)
my $LDAP = Net::LDAP->new( $Self->{Host}, %{ $Self->{Params} } );
if ( !$LDAP ) {
if ( $Self->{Die} ) {
die "Can't connect to $Self->{Host}: $@";
}
else {
$Self->{LogObject}->Log(
Priority => 'error',
Message => "Can't connect to $Self->{Host}: $@",
);
return;
}
}

[crythias]

ldap connects over port 389 or 636 (SSL) default. Check firewall, ports, nmap, telnet xxxx port