In the Carbon event model, the EventRecord has a field named "when". This field is not initialized for mouse events that are sent to NPP_HandleEvent; it has a garbage value. In the handlMouseEvent function in PluginViewMac.cpp, the "when" field isn't filled in. There are several places in this file where an EventRecord is created, and this is the only one that fails to initialize the when field. (Bug reported against Qt version 4.6.2)