Thanks for your help Steve, I think Otto is looking at the *real* problem.
You clearly don't understand the real problem. The SBL and XBL are two different lists. Your spamd configuration uses the SBL, and tarpits all hosts that appear on it. Your sendmail configuration uses both the SBL and XBL, and so the XBL hosts which do not appear in the SBL are blocked by sendmail. The two examples you gave are both listed in the XBL, but not the SBL, if you would do the IP lookup at spamhaus.org.
Your setup is working fine. Steve
