When a core is being customized or generated, certain actions in the core Information window are disabled. For example, the "Customize" action is grayed out and changed to "Customize (not available while carrying out another task)."
If a user starts to customize a core, but then cancels the process, the actions on the Information page are not re-activated.
The actions are still available by right-clicking on the core and selecting the desired option. Additionally, if you click on a different core and then re-select the desired core, the tasks are re-activated.
This issue is resolved in the ISE Design Suite 11.2 release.