This condition is usually caused by improper agentcmd usage. Use the following format for guidance:

agentcmd.exe -s -p <agent port> <agent hostname> "rexec <password in .uptmpasswd file> <unix path to script on agent host or (windows) script path in the registry>"

For Example:

agentcmd.exe -s -p 9998 sql2005 "rexec password cpu"

Where:
sql2005 = client hostname where the custom script resides
password = password value for the agent.CmdsPassword value
cpu = the name assigned to the script path in the Windows registry (i.e. cpu = cmd.exe /c c:\\scripts\\typecpu.bat)