If you install the Commerce Server starter site on a port other than port 80, you will run into a couple of issues. The problem is that Microsoft coded the site to drop the port number. To correct the problem, open the App_Code\SiteContext.cs file and comment out the following line of code (it's on line 247, for me):
builder.Port = -1; // Removes the port setting from the site.
Add the following line of code in its place (note, update port numbers to match your sites configuration):
builder.Port = secure ? 8443 : 8080;
The User\Login.aspx.cs file also needs to be updated. Located the following line in the OnInit() method and change the -1 to match the port number for which SSL is configured to run on your site:
builder.Port = -1; // Change this to your sites SSL port
Hope that helps...