Here's a link to my phpinfo : http://www.bullshido.net/gallery/phpinfo.php
I know this is a problem with my specific setup, not with the Photopost code per se. The interaction of something in my setup and Photopost is causing this, obivously, but I've tried exploring every avenue I could. Even twiddling with adm-misc.php to dump the $_POST/$_GET variables and exit yields a blank page. The other scripts that aren't using adm-misc.php seem to be working just fine, which is why it's a real stumper.
Oh, should also add, since this started happening, we've reinstalled photopost from the distribution archive. We did NOT remove the photopost database, however, since we have too much to rebuild. Given that fact, I'm inclined to say it's something within the DB that's causing it, but you've got me as to what that could possibly be.