We were able to get exchange RPC working over HTTP today. We went through the rigamarole of setting it up by hand, and that took a couple hours. And it didn't work. I did a google search (I don't know why I didnt' do that before we started) and found new instructions.
See, we had been looking at some msexchange.com or something website and following the instructions on there. I should have known better; always look at that Microsoft site first. If they don't have a step-by-step guide, then they don't want you to do it. Of course I found a guide, and the guide was a lot simpler because the process of RPC over HTTP is automated if you install service pack 1 (which we hadn't). Come to find out, there's a service pack 2 (how delinquint we are!). We installed that, followed the 3 steps that we had to follow, set up the client and we were good! It was actually a lot easier than I had imagined, once we went to the MS site for directions. Note to self: Always go to the Microsoft Knowledge Base First!