For anyone that hasn't listened to the podcast, this "slamdunk" that was found was an example where a GM
could say that a group of orcs
might lose track of an invisible mage in a situation where a barbarian was attacking them while screaming and a rogue had set off some kegs of gunpowder nearby. In other words, absolutely nothing different from what the rest of us have been saying -- in special circumstances, it's a GM's call.
The podcast this goes on to say that it would be perfectly normal and in accordance with the rules to say that creatures know the locations of everyone unless they hide, invisible or not.
I mean, you guy really want to say you've discovered my position (and
@iserith's, and
@Hriston's) and decided it vindicates you, I guess that this is a successful thread. The normal is you know where an invisible creature is, but special circumstances could arise where a GM might decide differently. Excellent well done.