Since I still support ASP.NET 1.1 clients as they migrate to ASP.NET 2.0, I come across this error frequently when working in my environments that support both versions of the .NET framework. "Auto-attach to process '[####] aspnet_wp.exe' on machine 'MACHINENAME' failed. Error code 0x8013134b." At first glance, it can be a troubling error, but the resolution is quite simple.

This error occurs when more than one .NET framework is installed, and IIS is set to run an application developed in one framework version using the other. There are tools one can install to make the switching between ASP.NET 1.1 and 2.0 easier, but it is just as simple to make the change in IIS.

In IIS, open up your website application, right-click and select properties, and choose the "ASP.NET" tab. Change the ASP.NET version to the appropriate version required by the project. Happy coding...