I have to support some legacy applications written in ASP.NET 1.1/VS2003.  I had to recently rebuild my workstation and now I'm seeing some strange behavior.

I cannot click the play button on the toolbar to run my web project in debug mode, if the start URL for the project contains my fully-qualified machine name.  I get the message saying:

"Error while trying to run project: Unable to start debugging on the web server.  You do not have permissions to debug the server.  Verify that you are a member of the 'Debugger Users' group on the server.

I checked, I am a member of that group.

I can run it without debugging and then attach the debugger to the aspnet_wp.exe and then I can debug the project.

If I change the start URL to localhost, I can debug by clicking the play button.

I am impersonating a domain user account, and this is set up in the web config and has not changed.

The problem I have is that this application relies on a different web application for authentication, so if start it from localhost, my login is successful, but I can't navigate away from the login page as I am not in the same domain as the app that authenticated me.  Because of this, I have to use the fully qualified machine name.

As I can manually attach the debugger, I'd like to be able to get the play button working.  I am not sure why it works one way and not the other.

I'm trying to debug using IIS on my local PC.  There is no separate server involved.

 Are you running a version of Windows that allows the Visual Studio debugger to automatically attach to a Web application? If not, you need to launch the application without debugging and manually attach to it. (For more information, see Manually Attaching and ASP.NET Debugging: System Requirements.)

Refer to: http://msdn.microsoft.com/en-us/library/dwesw3ee(VS.80).aspx

Try installing this:

http://www.microsoft.com/downloads/details.aspx?FamilyId=049C9DBE-3B8E-4F30-8245-9E368D3CDB5A&displaylang=en

The workstation already has SP3 installed.

I finally figured it out.  To reiterate, I had to set the start URL to my fully qualified machine name in order for it to work with the authentication we are using.  I could not run the debugger by starting fromt he menu (F5 or play button).  However, if set my start URL to be localhost, it worked fine.  This lead me to believe it was a permission issue of some sort.