"An unexpected error has occurred" on all the SharePoint Server 2010 sites.

Issue:
All SharePoint sites throw the following error:
"An unexpected error has occurred."

Errors:
In ULS logs, something similar can be found

An exception occurred when trying to issue security token: The server was unable to process the request due to an internal error. For more information about the error, either turn on IncludeExceptionDetailInFaults (either from ServiceBehaviorAttribute or from the configuration behavior) on the server in order to send the exception information back to the client, or turn on tracing as per the Microsoft .NET Framework 3.0 SDK documentation and inspect the server trace logs.. 

Exception occured while connecting to WCF endpoint: System.ServiceModel.FaultException: The server was unable to process the request due to an internal error. For more information about the error, either turn on IncludeExceptionDetailInFaults (either from ServiceBehaviorAttribute or from the configuration behavior) on the server in order to send the exception information back to the client, or turn on tracing as per the Microsoft .NET Framework 3.0 SDK documentation and inspect the server trace logs. 
at Microsoft.IdentityModel.Protocols.WSTrust.WSTrustChannel.ReadResponse(Message response) 
at Microsoft.IdentityModel.Protocols.WSTrust.WSTrustChannel.Issue(RequestSecurityToken rst, RequestSecurityTokenResponse& rstr) 
at Microsoft.IdentityModel.Protocols.WSTrust.WSTrustChannel.Issue(RequestSecurityToken rst) 
at Microsoft.SharePoint.SPSecurityContext.SecurityTokenForContext(Uri context, Boolean bearerToken, SecurityToken onBehalfOf, SecurityToken actAs, SecurityToken delegateTo) 
at Microsoft.SharePoint.SPSecurityContext.<>c__DisplayClass7.b__6() 
at Microsoft.SharePoint.Utilities.SecurityContext.RunAsProcess(CodeToRunElevated secureCode) 
at Microsoft.SharePoint.SPSecurityContext.GetProcessSecurityTokenForServiceContext() 
at Microsoft.SharePoint.SPChannelFactoryOperations.CreateChannelAsProcess[TChannel](ChannelFactory`1 factory, EndpointAddress address, Uri via) 
at Microsoft.SharePoint.SPChannelFactoryOperations.CreateChannelAsProcess[TChannel](ChannelFactory`1 factory, EndpointAddress address) 
at Microsoft.Office.Server.UserProfiles.MossClientBase`1.get_Channel() 
at Microsoft.Office.Server.UserProfiles.MossClientBase`1.ExecuteOnChannel(String operationName, CodeBlock codeBlock) 
at Microsoft.Office.Server.UserProfiles.ProfilePropertyServiceClient.ExecuteOnChannel(String operationName, CodeBlock codeBlock)

UserProfileApplicationProxy.InitializePropertyCache: Microsoft.Office.Server.UserProfiles.UserProfileException: The server was unable to process the request due to an internal error. For more information about the error, either turn on IncludeExceptionDetailInFaults (either from ServiceBehaviorAttribute or from the configuration behavior) on the server in order to send the exception information back to the client, or turn on tracing as per the Microsoft .NET Framework 3.0 SDK documentation and inspect the server trace logs. ---> System.ServiceModel.FaultException: The server was unable to process the request due to an internal error. For more information about the error, either turn on IncludeExceptionDetailInFaults (either from ServiceBehaviorAttribute or from the configuration behavior) on the server in order to send the exception information back to the client, or turn on tracing as per the Microsoft .NET Framework 3.0 SDK documentation and inspect the server trace logs. 
at Microsoft.IdentityModel.Protocols.WSTrust.WSTrustChannel.ReadResponse(Message response) 
at Microsoft.IdentityModel.Protocols.WSTrust.WSTrustChannel.Issue(RequestSecurityToken rst, RequestSecurityTokenResponse& rstr) 
at Microsoft.IdentityModel.Protocols.WSTrust.WSTrustChannel.Issue(RequestSecurityToken rst) 
at Microsoft.SharePoint.SPSecurityContext.SecurityTokenForContext(Uri context, Boolean bearerToken, SecurityToken onBehalfOf, SecurityToken actAs, SecurityToken delegateTo) 
at Microsoft.SharePoint.SPSecurityContext.<>c__DisplayClass7.b__6() 
at Microsoft.SharePoint.Utilities.SecurityContext.RunAsProcess(CodeToRunElevated secureCode) 
at Microsoft.SharePoint.SPSecurityContext.GetProcessSecurityTokenForServiceContext() 
at Microsoft.SharePoint.SPChannelFactoryOperations.CreateChannelAsProcess[TChannel](ChannelFactory`1 factory, EndpointAddress address, Uri via) 
at Microsoft.SharePoint.SPChannelFactoryOperations.CreateChannelAsProcess[TChannel](ChannelFactory`1 factory, EndpointAddress address) 
at Microsoft.Office.Server.UserProfiles.MossClientBase`1.get_Channel() 
at Microsoft.Office.Server.UserProfiles.MossClientBase`1.ExecuteOnChannel(String operationName, CodeBlock codeBlock) 
at Microsoft.Office.Server.UserProfiles.ProfilePropertyServiceClient.ExecuteOnChannel(String operationName, CodeBlock codeBlock) -
-- End of inner exception stack trace --- 
at Microsoft.Office.Server.UserProfiles.ProfilePropertyServiceClient.ExecuteOnChannel(String operationName, CodeBlock codeBlock) 
at Microsoft.Office.Server.UserProfiles.ProfilePropertyServiceClient.GetProfileProperties() 
at Microsoft.Office.Server.Administration.UserProfileApplicationProxy.RefreshProperties(Guid applicationID) 
at Microsoft.Office.Server.Utilities.SPAsyncCache`2.GetValueNow(K key) 
at Microsoft.Office.Server.Utilities.SPAsyncCache`2.GetValue(K key, Boolean asynchronous) 
at Microsoft.Office.Server.Administration.UserProfileApplicationProxy.InitializePropertyCache()

System.NullReferenceException: Object reference not set to an instance of an object. 
at Microsoft.Office.Server.Administration.UserProfileApplicationProxy.get_ApplicationProperties() 
at Microsoft.Office.Server.Administration.UserProfileApplicationProxy.get_PartitionIDs() 
at Microsoft.Office.Server.Administration.UserProfileApplicationProxy.IsAvailable(SPServiceContext serviceContext) 
at Microsoft.Office.Server.WebControls.MyLinksRibbon.get_PortalAvailable() 
at Microsoft.Office.Server.WebControls.MyLinksRibbon.EnsureMySiteUrls() 
at Microsoft.Office.Server.WebControls.MyLinksRibbon.get_PortalMySiteUrlAvailable() 
at Microsoft.Office.Server.WebControls.MyLinksRibbon.OnLoad(EventArgs e) 
at System.Web.UI.Control.LoadRecursive() 
at System.Web.UI.Control.LoadRecursive() 
at System.Web.UI.Control.LoadRecursive() 
at System.Web.UI.Control.LoadRecursive() 
at System.Web.UI.Control.LoadRecursive() 
at System.Web.UI.Control.LoadRecursive() 
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

Cause:
This will occur on single server deployments which uses build in SQL database. If you have done a farm installation, the resolution/cause may not apply.

Forefront Identity Manager Synchronization service corrupt not working. This in turn affects User profile sync service and security token service application.

If your applications are associated with User profile service, you will get the error.

Resolution:
As per the Technet article, User profile synchronization service does not work with single server deployment with build in databases.
Check the article for further details:
http://technet.microsoft.com/en-us/library/cc263202.aspx

To resolve the issue, delete the User profile synchronization service instance from Central Admin.