When you access the error profiles in the Management page an error will appear:
"An error occurred in the K2_Management Service Instance. Object cannot be cast from DBNull to other types."
This is related to a new column added to: [K2].[Server].[ErrorProfile]
Column name: [ThresholdRule]
If the value is NULL then you cannot load the error profiles.
As a workaround, please update the ThresholdRule using the following script:
Set ThresholdRule = -1
Where ID = [ID]
Install the latest cumulative update and fix pack to resolve this error.