OpenDKIM - too many errors after DATA

Servus zusammen,

ich hab hier ein eigenartiges Problem mit OpenDKIM in Kombination mit Postfix:

Jul 19 15:05:00 smart1 postfix/smtpd[23003]: too many errors after DATA from XXXX[192.188.25.6]

Das Problem tritt ungefähr 3595 mal am Tag auf, wir versenden rund 100-160 E-Mails die Minute,
die Vermutung das es ein Resourcenproblem ist liegt somit nahe, ein versuchtes nice -19 auf den
OpenDKIM Prozess brachte jedoch auch keine Besserung.

Integration Details:
OS: Linux 2.6.32-220.17.1.el6.x86_64 #1 SMP Thu Apr 26 13:37:13 EDT 2012 x86_64 x86_64 x86_64 GNU/Linux
CPU: Intel(R) Xeon(R) CPU X5650 @ 2.67GHz
RAM: 48GB

Postfix main.cf

smtpd_banner = $myhostname ESMTP - Spamfilter
biff = no
append_dot_mydomain = no
readme_directory = no

myhostname = email.mydomain.at
myorigin = mydomain.at
mydestination =
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 192.168.0.0/24
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all


mydestination = $myhostname
transport_maps = hash:/etc/postfix/transport
relay_domains=mydomains.com


## dkim
smtpd_milters = inet:localhost:8891

smtpd_sender_restrictions = check_policy_service inet:127.0.0.1:10040, permit_mynetworks, permit_sasl_authenticated , permit_mynetworks, reject_unauth_destination, permit_mynetworks,permit_sasl_authenticated,reject_unauth_destination
smtpd_recipient_restrictions = check_policy_service inet:127.0.0.1:10040, permit_mynetworks, permit_sasl_authenticated , permit_mynetworks, reject_unauth_destination, permit_mynetworks,permit_sasl_authenticated,reject_unauth_destination
stmpd_hard_error_limit=30