First of all, make sure you’re application pool is running the correct .NET Version:
- .NET 2.0, 3.0 and 3.5 web applications, should use an application pool that uses .NET 2.0
- .NET 4.0 web application, should use an application pool that uses .NET 4.0
Now, based on the configuration and error, it looks like: Visual Studio 2008 is running under WOW64 on your 64 bit machine and thus it needs remote debugging to connect between WOW64 and the 64-bit application on machine. Thus, to debug on the 64 bit machine, you might need to make sure the remote debugging components are installed correctly. Following article should help:
MSDN: How to: Debug 64-Bit Applications[
^]
If that does not help, post it, follow this MSDN article to troubleshoot it and see if it helps:
MSDN: Error: Unable to Start Debugging on the Web Server[
^]