Nearly two weeks after reporting the problem, they still have not been able to get removed from the Spamhaus blacklist. Seems Monsterhost does not understand they have to do more than just request to be removed. They have to fix the problems, FIRST! Spamhaus makes this very clear on their webpages.
Update: We had several rounds of trying to report my IP to get off the Spamhaus list, before I realized they were giving me a new IP each time! So rather than fixing the problem, reporting had no effect. They had suggested I pay for a dedicated IP address which would be free of spam by other users. I talked them into paying for it. So it is working now... well, after adding a PTR record, which they helped me with. So I've bumped them up to two stars, simply because this should not have taken weeks to resolve. Still, things are working ok now and the cost is pretty good.