Accessing to FIM Portal - Unable to process your request

Hi

I am facing an issue where users can't access to the FIM Portal. It doesn't matter are you a normal user or admin. The error message is allways the same, "Unable to process your request".

Also I have managed to get a Detailed error message from the portal but it does point me to nowhere. It is below:

Server Error in '/' Application.
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Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:


[NullReferenceException: Object reference not set to an instance of an object.]
   Microsoft.IdentityManagement.WebUI.Controls.UICacheUtils.GetCacheKey(CacheKey key) +274
   Microsoft.IdentityManagement.WebUI.Controls.NavigationBarConfigurationModel.RetrieveSiteNodeFromCache() +118
   Microsoft.IdentityManagement.WebUI.Controls.NavigationBarProvider.BuildSiteMap() +63
   Microsoft.SharePoint.WebControls.AspMenu.AdjustForProviderMaximumDepth() +90
   Microsoft.SharePoint.WebControls.AspMenu.OnPreRender(EventArgs e) +49
   System.Web.UI.Control.PreRenderRecursiveInternal() +154
   System.Web.UI.Control.PreRenderRecursiveInternal() +239
   System.Web.UI.Control.PreRenderRecursiveInternal() +239
   System.Web.UI.Control.PreRenderRecursiveInternal() +239
   System.Web.UI.Control.PreRenderRecursiveInternal() +239
   System.Web.UI.Control.PreRenderRecursiveInternal() +239
   System.Web.UI.Control.PreRenderRecursiveInternal() +239
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +4105



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Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.34248 

Any ideas what to do next?