Auto-attach to process ‘[2440] w3wp.exe’ on machine ‘…’ failed. Error code 0x8013134b. This problem is most likely occurred because I have two .NET framework installed in my PC (v1.14322 and v2.0).

To fix this problem:

• Open IIS (inetmgr)
• Right click on the web site with the problem
• Click the ASP.NET tab
• Change the ASP.NET version from 2.something to 1.14322 in the dropdown(or vice versa) and debugging works again