The reasons for this error are manysome!

Is it related to the WebLogicServer targets? Try this

Is it related to a listener?<br /> Under the Errors sub-tab, the error message reads “Target is in broken state. Reason - Compute dynamic property takes too long”?<br /> From:<br /> Oracle® Enterprise Manager<br /> System Monitoring Plug-in Troubleshooting Guide<br /> Release 12 (12.0)<br /> E10314-11<br /> November 2010<br />

Cause<br /> This behavior occurs when target, agent, or both and/or target system become slow or heavily loaded and computation of dynamic properties take longer than the default timeout value. Workaround<br /> Execute the following command: emctl reload agent dynamicproperties <target name»<target type> OR<br /> You can alternatively resubmit the target instance properties: *Click on the Monitoring Configuration link (under the Related Links section on the plug-in target home page). *Re-enter the encrypted properties. *Click OK.Try re-confirming the listener configuration page (without making any changes): OR<br /> Targets : All Targets Search for “Listener” Click the radio button next to the listener that's not up and click the “Configure” button. Check the details are ok and click “OK”