This is bug originally reported against NetBeans, for details please see
http://www.netbeans.org/issues/show_bug.cgi?id=96189
It seems that on systems with special trackball, isPopupTrigger returns true in situations where it should not.
HW description - trackball with three buttons and a fourth button that
makes the mouse/trackball scroll instead of move the pointer, i.e. holding that
button transforms the trackball wheel into a scroll wheel (really nifty).
Scrolling with fourth button pressed works okay, but after maybe half a second it pops up a context menu, as if the second mouse button was pressed, which wasn't.
I'm attaching small test application. Original reporter (added to interest list) confirms that problem can be reproduced 100% on his trackball with this test app.
I'll ask original reporter to add detail info about his trackball HW and java version...