After upgrading client tasks immediately fail with Unable to get a .NET type error message

Products

• IT Management Suite
• Task Server
• Software Management Solution

Issue/Introduction

After scheduling a task clients immediately fail with Unable to get a .NET type error message

An unknown exception was thrown.
 
Show raw exception message
System.Exception: SerializedParameterCollection::ToValue(): Unable to get a .NET type named Altiris.TaskManagement.Common.Tokens.TokenDefinitionCollection, Altiris.TaskManagement.Common, Version=7.5.XXXX.XX (Latest Version), Culture=neutral, PublicKeyToken=99b1e4cc0d03f223 at Altiris.DotNetLib.Collections.SerializedParameterCollection.ToParameterValueCollection() at Altiris.ClientTask.Server.Data.ClientTaskServerExecutionInstance.get_InputParameterValues() at Altiris.ClientTask.Server.Execution.ClientTaskEngineExecutionThread.LoadInputParametersFromTaskInstanceParent() at Altiris.ClientTask.Server.Execution.ClientTaskEngineExecutionThread.Execute() at Altiris.TaskManagement.Common.Execution.Engine.TaskExecutionEngine.ProcessTaskExecuteOperation(TaskInstanceRequest request, TaskEngineExecutionThread thread)

Cause

This error will come up when attempting to execute tasks on already upgraded client that registered to not yet upgraded Task Server” (i.e. client version > than Task Server version)

The agent software package within the Policy has been updated. However, the Policy GUID appears to have remained the same.
This means that the servers never obtain a "new" policy to execute on the Run Once ASAP schedule.

Resolution

Upgrade the Task Server to the correct version. 
Check to make sure your Task Servers are up to date as well. The upgrade policy is in Settings > All Settings > Notification Server > Site Server Settings > Task Service > Advanced.

The Task Server upgrade policy will only apply to a server if the Management Agent is on the latest version as well. In addition to checking the Task Service upgrade policy, check the Agent Upgrade policy in: 

Settings > All Settings > Agent/Plug-ins>Symantec Management Agent>Windows>Site Server.

After an upgrade to any new version, add a new schedule to these two policies and enable them. Once the task service is upgraded tasks should start working correctly.