Someone from Ultima would need to confirm, but I believe they are running 100% Windows (no Apache), so at the minimum you should probably run IIS. This may identify/resolve the discrepancies between your local environment and the hosting server(s).
Additionally, if you have to install something on your computer to get your application to work (such as an Add-on component), that usually needs to also be installed on the hosting server, however most hosting companies do not allow you to install anything on the server (unless you have a dedicated server).
William Eaton, MCSE
iTech Computer Solutions, LLC
www.itechcs.com