Hi Lukasz,
When you run the patch assessment on the client, what are the errors in the logs for the SMA?
Can you also confirm if the patch assessment package that is on these broken machines matches the patch assessment package of a working machine? I've provided my versions below to compare to if required. The package can be found at: C:\Program Files\Altiris\Altiris Agent\Agents\SoftwareManagement\Software Delivery\{6D417916-467C-46A7-A870-6D86D9345B61}\cache
Open AexPatchAssessment.exe and check the version in the details tab.
My AexPatchAssessment.exe version: 7.2.2566.0
Can you also check that the MetaData Import Task is running successfully?
Thanks