You might be unable to view the alarm definitions for a data center object in the vSphere Web Client.
When you click the Alarm Definitions tab on the Manage tab of a data center, the tab appears darkened by a translucent overlay and no error message appears.
Inability to view the alarm definitions might be caused by insufficient memory. Problems that occur on the vCenter Server side should result in an error message, but lack of available memory for Adobe Flash Player on the client machine prevents the error notification dialog from appearing.
For hardware requirements, see vSphere Installation and Setup.