This link explains how to troubleshoot Remote Access for your MediaSmart or Windows Home Server:
IMPORTANT - MUST READ: If you have any
other routers on your network. This
includes DSL or Cable modems with
built-in routers, Vonage or other IP
Phone devices this could be the cause
of your trouble. You can try to set
the DMZ from the Vonage or VOIP, DSL
or Cable device to your router and
then try the MS Router config again.
This could solve your issue.
have a vonage router that is in FRONT
of your normal router, you can try to
move the vonage device behind the
router. Make sure you reboot your
cable modem, router and vonage device
(in that order pausing 1 min before
powering up each device). Make sure
the MediaSmart server is connected to
the normal router and not the vonage
device (unless that’s your setup)
If you'll get an "Verifying that your remote web site is available from the internet" error on configuring your router, read this Microsoft forums thread:
I had the same problem which had kept me busy for two days. Just found the solution on the internet. First unconfigure both the router and domain. Then configure the domain first end the router afterwards.
Could it be the case that you're looking for the problem on the wrong end? Could it be that you aren't allowed to connect from your remote location?
If your router model is a UPnP-certified device and if the router UPnP setting is enabled, Windows Home Server can automatically configure it. See this Microsoft support article: Information about the automatic router configuration feature in Windows Home Server.
If the latter method doesn't work with your router model, try forwarding following ports that in order to enable remote access: TCP 80, 443 and 4125 to the local IP address of your Windows Home Server.