Please review the following steps and verify that you have a similar issue.

Try to manually run the file from the following path.
C:\Program Files\Altiris\Altiris Agent\Agents\SoftwareManagement\Software Delivery\{6D417916-467C-46A7-A870-6D86D9345B61}\cache
Filename: AexPatchAssessment.exe

1. Verify the correct installation path of SMP agent installed on Client computer.

2. Verify that Queue folder exists i.e. C:\Program Files\Altiris\Altiris Agent\Queue

3. Verify that the following regkey has to correct value

HKEY_LOCAL_MACHINE\SOFTWARE\Altiris\Altiris Agent\Transport\Queue Path
Value: C:\Program Files\Altiris\Altiris Agent\Queue
 

In our case, customer had an Older version of Altiris Ver6 still installed on the Server in the following directory.

C:\Program Files (x86)\Altiris\Altiris Agent\

Since correct SMP agent version i.e. 7.1 SP2 agent was installed within C:\Program Files\Altiris\Altiris Agent\ except for inventory agent, we cleared out all files and directories from

C:\Program Files (x86)\Altiris\Altiris Agent\ leaving ONLY C:\Program Files (x86)\Altiris\Altiris Agent\Agents\inventory Agent (as this is a valid folder)

Having incorrect files & reference in Registery was causing agent not to process information correctly.

After removing older files, we restarted SMP agent and ran Windows Assessment scan and it returned a success code.

Related KBs

Title: Windows Assessment Scan Error Codes
http://www.symantec.com/docs/TECH179849 

Title: Windows System Assessment Scan fails with Exit Code 6
http://www.symantec.com/docs/TECH182272

Title: Windows System Assessment Scan displays failed with Exit Code 3
http://www.symantec.com/docs/TECH185079