I'm not sure what's happening to cause the demos to crash but, make sure you have the latest version of DBP installed also try re-installing (worth a try if all else fails). Another possible cause of the problem, have you registered the plug-in properly?
As for the pathfinding demo, you have to click somewhere on the geometry, this will then cause the A.I system to find a path from the current location to the point you clicked. If you press F1 the demos will display usage instructions.
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