If your site is on shared hosting, it could be that one of your neighbors is a spammer.
There is one thing, that I know of, that you can do to try to get off of the list. If you are certain that you are not spamming people, then you can create one or more blogs (obviously your tracks should be well covered), and get Akismet running on them. Go ahead and make your comments on these blogs. Akismet should flag them, so they won't show up, but whent Akismet does this, it holds on to the "spam" for two weeks. You can go in and flag these as "false positives".
The more blogs the better, and the more seasoned they are, the better. If you are making decent money, you might want to consider purchasing seasoned blogs for this purpose. You might also go for some more "organic" results, by contacting bloggers, and respectfully asking them to go and flag your posts as false positives.
Finally, and don't take this the wrong way, I would do some serious self analysis about the quality of the posts that you are putting out there. Just because a post is friendly, and on topic, if it does not contribute meaningfully to the discussion, and it contains an outbound link, a lot of bloggers will get pissed. Since it sounds like you are engaged in direct promotion of your site, that means that you are completely at their mercy, so it is all on you to bend over backwards not to piss anyone off. If you can't get off the blacklist, or you get off only to get back on, then you might seriously want to consider a more indirect method of promotion, so that you don't mess up your "real" site when some overly sensitive blogger decides to flag you because they are a picky snob.