If i'm not mistaken Discountasp offers iis7 hosting. You can ask for an upgrade and that should take care of your problem. In IIS7 you can register an asp.net httpmodule directly to IIS in the web.config file. The asp.net mvc web.config already comes with this configured and you should have no problem running in iis7.
another option which is not very elegant and may slow your server is to rout all traffic to the asp.net isap dll. this slows performance but it was the only thing that worked for me in server 2003 with iis6.