This one is a well known error for people who have worked with CRM 4.0 and an easy fix was to restart CRM Async Service.
The key specified to compute a hash value is expired, only active keys are valid. Expired Key : CrmKey(Id:a06a2c71-e96a-e011-ae0c-000c29ce8648, ScaleGroupId:00000000-0000-0000-0000-000000000000, KeyType:CrmStaticVersionScaleGroupKey, Expired:True, ValidOn:04/20/2011 00:59:35, ExpiresOn:06/19/2011 00:59:35, CreatedOn:04/20/2011 00:59:35, CreatedBy:CRM\Administrator.
The same error when it comes to CRM 2011, you might have to restart
Microsoft Dynamics CRM Asynchronous Processing Service
Microsoft Dynamics CRM Asynchronous Processing Service (maintenance)
followed by an IIS Reset.