You can experience these symptoms when you are using Microsoft Dynamics CRM 4.0 with Windows 2008 and try to logon via web browser. Also the URL is correct (for example http://machine:5555), you will receive an error message in your browser.

HTTP Error 404.15 – Not Found
The request filtering module is configured to deny a request where the query string is too long.

Also the error message will indicate that the entered URL is too long, and this may not be the underlying root cause of the problem.
The URL length could be rebuilt due to redirection of IIS and result in exceeding the request limit. Also when you increase the request limit according to the following Knowledge Base, you are still unable to logon into CRM.

Error message when you visit a Web site that is hosted on a server that is running IIS 7.0: "HTTP Error 404.15 – Not Found"
http://support.microsoft.com/default.aspx?scid=kb;EN-US;942071

Reason for this could also be, that the user account trying to login does not exist in CRM.

In this situation you should find a warning in your application event log from source “ASP.NET 2.0.50727.0”.

Event code: 3005

Event message: An unhandled exception has occurred.

Exception information:

Exception type: CrmException

Exception message: No Microsoft Dynamics CRM user exists with the specified domain name and user ID

Stack trace:
at Microsoft.Crm.Authentication.WindowsAuthenticationProvider.QueryForOrganizationId(String userToken)
at Microsoft.Crm.Authentication.WindowAuthenticationProviderBase.Authenticate(HttpApplication application)
at Microsoft.Crm.Authentication.AuthenticationStep.Authenticate(HttpApplication application)
at Microsoft.Crm.Authentication.AuthenticationPipeline.Authenticate(HttpApplication application)
at Microsoft.Crm.Authentication.AuthenticationEngine.Execute(Object sender, EventArgs e)
at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

In addition you could also find similar entries in the IIS log.

2012-02-16 08:22:34 ::1 GET /default.aspx - 5555 - ::1 Mozilla/5.0+(compatible;+MSIE+9.0;+Windows+NT+6.0;+WOW64;+Trident/5.0) 401 2 5 21

2012-02-16 08:22:34 ::1 GET /default.aspx - 5555 - ::1 Mozilla/5.0+(compatible;+MSIE+9.0;+Windows+NT+6.0;+WOW64;+Trident/5.0) 401 1 2148074254 1

2012-02-16 08:22:36 ::1 GET /_common/error/errorhandler.aspx ErrorCode=0x80040354&RequestUri=%2fdefault.aspx&BackUri= 5555 - ::1 Mozilla/5.0+(compatible;+MSIE+9.0;+Windows+NT+6.0;+WOW64;+Trident/5.0) 401 1 2148074254 74

 

To resolve this problem, logon to Dynamics CRM with an administrative account first. Add the user account failing to logon to CRM as new CRM user. Finally add a security role to the new created CRM user account. Now the user account should be able to login without error.

More Information

Request Limits
http://www.iis.net/ConfigReference/system.webServer/security/requestFiltering/requestLimits

The HTTP status codes in IIS 7.0 and in IIS 7.5
http://support.microsoft.com/default.aspx?scid=kb;EN-US;943891

 

Best Regards

Dynamics CRM Team