This issue was detected on v11.1 in December, 2011, according to Etrack 2636025. A fix will be included in a future version.
The Endpoint Agent performs keyword or protocol monitoring and generates incidents, which are transmitted back to the Endpoint Server. The Agent is unable to process EDM/IDM rules, so it cracks the information for later detection on the Endpoint Server. As a result, the EP server, running the EDM/IDM rule, detects the same violations and creates a second incident for the same violation.