When the core is upgraded from 126.96.36.199 to 188.8.131.52, it gets an error similar to the following on the core Home tab and clicking on Alerts in the Events tab:
ERROR 2015-03-09T16:16:49  - WCFClientBase.EncapsulatedException () Caught an exception deserializing encapsulated exception of type 'System.AggregateException'
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.Runtime.Serialization.SerializationException: Member 'IsImportant' was not found.
When the agents were upgrade to match the core, the above reported core UI error reflects the same error is persistent.