VS2010 Error: "Unable to start debugging on the web server"

Gary Davis
Gary Davis used Ask the Experts™
I get error message "Unable to start debugging on the web server" in Visual Studio 2010. I clicked the Help button and followed the related suggestions without success.

This happens with a newly created local ASP.Net project when modified to use IIS instead of Cassini (which works for debugging). It prompts to set debug="true" in the web.config and then immediately pops up the error. Nothing shows up in the Event Viewer.

I am able to attach to w3wp to debug. It works but is not as convenient as F5.

I also have a similar problem with VS2008 on the same PC. Debugging used to work for both.

I have re-registered Framework 4 (aspnet_regiis -i). I ran the VS2010 repair (this is the RTM version). I am running on a Windows Server 2008 R2 x64 box.

I do have Resharper V5 installed.

There must be some configuration setting or registry value that survives the repair causing the problem.

I'd appreciate any ideas.

Thanks, Gary Davis (garyd@webguild.com)
Watch Question

Do more with

Expert Office
EXPERT OFFICE® is a registered trademark of EXPERTS EXCHANGE®
Mohamed OsamaSenior IT Consultant

UAC related perhaps ?
are you running Visual studio as administrator?
Gary DavisDir Internet Svcs


Running as adiministrator did not help. I have UAC disabled, too.
Dir Internet Svcs
Solution found that works for me:
  1. In Regedit, navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
  2. Right-click Lsa and create a new DWORD value
  3. Name it DisableLoopbackCheck
  4. Set its value to 1
  5. Reboot (instead, I killed the msvsmon.exe process and restarted Visual Studio)
Details at my blog.

Do more with

Expert Office
Submit tech questions to Ask the Experts™ at any time to receive solutions, advice, and new ideas from leading industry professionals.

Start 7-Day Free Trial