Currently when an alert is set to fire once and then disable yourself, it is hard for an administrator to re-enable it. On the dashboard you can click on the alert name to see the one alert instance or on the definition to see its definition. Clicking on the alert lets the user delete it, but not re-enable it. Clicking on the defiition lets the user re-enable it, but not delete the alert instance. There should be a "delete & enable" button on the alert instance if the alert has been disabled (due to firing).
This bug was previously known as http://jira.rhq-project.org/browse/RHQ-1879
mass add of key word FutureFeature to help track
While not directly implemented it this way, there is now with BZ 535889 the possibility to first enable the definition on the alert detail page and then with a 2nd click on the same page delete this fired alert instance. While I initially proposed this as a user feedback, I don't think we need to make this 1-click, as the user will with the current implementation stay on the same page and does not need to remember where to go and click anymore. So I propose to close with WONTFIX
QA Closing as WONTFIX - see bug #535889