Confirm the scope of the issue.
Determine if the problem is confined to just 1 user or type of command.
Try running a test job as administrator and specify the FULL path to an exe.
Compare the agentparm.txt file with a working system in your environment to help rule out any agentparm.txt file issues.
Past cases have been reported to CA with similar exit codes of C0000142
Some of those cases were resolved via:
Restarting the agent
Restarting the host (reboot)
Taking off the interactive flag in the job definition.
Setting: oscomponent.logon.batch.first=true in the agentparm.txt and restarting the agent.
Disabling virus scanners that were causing issues.