While researching another issue in response to a thread in this forum, I had occasion to read up a bit on enable-force-cgi-redirect. While I could well be wrong on this, it seems as though this being set (with SERVER["REDIRECTSTATUS"] and REDIRECT_STATUS set to 200), in conjunction with Dreamhost suEXEC php binary setup may have something to do with what you are encountering. Both Dreamhost's PHP4 and PHP5 cgi binaries are configured this way. If this is impacting your code, it would appear that either configuring your own php.ini, tweaking .htaccess, or a combination of each of these techniques might provide a solution.
Please be gentle with me, as I am still wading (repeatedly) through the PHP documentation/notes regarding force-cgi-redirect and have now confused myself almost as much as I have educated myself. While this may not be relevant, my "sense" of what I'm reading makes me think that it might be, so I thought I would share that thought hoping that your greater understanding of the issue might either enable you to eliminate the possibility out of hand, or allow you to make better sense out of documentation than I have.
Obviously, I might be way off base here, but you might want to investigate as to whether or not this might be an issue impacting your code.
Hopefully one of the PHP wizards that hang out here can quickly post to tell me I don't have a clue on this if that, in fact, is the case!