Well, if the port indicates you are using the built-in web server (the one that comes with VS), this probably works because that always routes requests through the ASP.NET framework.
Requests ending with /abc will not automatically route through the ASP.NET framework because IIS may not "know" you want them to. You need to check your IIS settings to make sure such requests are routed to the aspnet_isapi.dll
EDIT: To accomplish this, you need to add a wildcard mapping:
In IIS Manager, expand the local computer, expand the Web Sites folder, right-click the Web site or virtual directory that you want, and then click Properties.
Click the appropriate tab: Home Directory, Virtual Directory, or Directory.
In the Application settings area, click Configuration, and then click the Mappings tab.
To install a wildcard application map, do the following:
On the Mappings tab, click Add or Insert.
Type the path to the DLL in the Executable text box or click Browse to navigate to it (for example, the ASP.NET 2.0 dll is at c:\windows\microsoft.net\framework\v2.0.50727\aspnet_isapi.dll on my machine)
For extension, use ".*" without quotes, of course
Select which verbs you want to look for (GET,HEAD,POST,DEBUG are the usual for ASP.NET, you decide)
Make sure "Script engine" or "Application engine" is selected
Uncheck "Check that file exists"
Click okay.
I may be off on this, but if I am, hopefully someone will correct me. :)
