- Close down all open Visual Studio IDE’s
- Go to the ASP.NET Temporary folder for the version of the framework under which your application pool is running. For my web service running as a ASP.NET 2.0 application this is located at <%systemroot%>Microsoft.NetFrameworkv2.0.50727Temporary ASP.NET Files.
- Delete the folder for your application.
- Reset IIS
- Check that you can now browse to your page, or web service, using IE.
- Then reopen your solution within the development environment.
Problem solved! No more Mutex errors and I could debug my web service in my development enviroment. If you are interested, there is a useful Wikipedia article on Mutual Exclusion.