inconsistent leak finding
I'm observing some inconsistent finding of leaks that seems to be a bug in Hammer. I'm wondering if anyone recognizes this behavior.
I recently added a new section of the map, and upon compiling I was warned that an object was located in the void. I checked carefully, and, because it was a small area, I'm quite confident there were no leaks. Nevertheless, I blocked off this new area by expanding an existing brush to seal it off. Now the map compiled. Confused, I undid this change (control-Z), and tried to compile again. To my surprise, the map compiled!
summary:
original state -- complained of object in void
sealed new area -- compiled
undid seal -- compiled
Although the Undo command has some issues, I'm willing to believe it can handle as simple a change as extending a brush. So the same map sometimes has a leak, and sometimes not.
Has anyone seen this before? Do you know what's going on?
no idea what went wrong.
But the easiest way to find leaks is after a failed compile go to map -> load point file and just follow the red line! That's the easiest way!
Brush entities have an 'origin point' (the purple dot in the middle of them); If, for some reason, you accidentally dragged that origin point outside the map it'll be considered as a leak, and if you accidentally dragged it back in then it won't leak.
Select all your brush entities and see if their origin point is not in the brush.
https://developer.valvesoftware.com/wiki/Leak
This article might help. There's a few common causes of leaks there. Maybe you accidentally moved an areaportal?
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Good suggestions, but I'm afraid they haven't resolved the issue. The error is that an object is located in the void, so loading the point file shows a red line indicating a random object in my map. I checked my brush entities, and both have origin points located squarely inside. The leak article is a nice summary, but my core problem is a bit different.
My problem is that exactly the same map sometimes has a leak, and sometimes not. The workaround I'm currently using is what I described above (seal off the new area, compile, undo, compile again). It's a little tedious, but gets the job done. I guess I just wanted to vent about that. 
I had the some problem with one of my first maps.
I was able to move or rotate the camera inside 3D-view to make it compile or not compile.
So I did not even try to fix the "invisible" leak, I just used different camera angles.
In my case, I was able to fix that problem with "center origins" command.
Since I know how to prevent leaks like this, I never got them again.
I know at one point I had some trouble with a corrupt entity (an invisible, unselectable, unwanted entity) causing leaks. I dont know if this is also the cause of your problems, but the way to fix it was to select everything in the map and copy it to a new map, which then worked perfectly. I hope this helps.
I think in terms of boolean variables. Generally, it makes things easier.
Yep, I've had this also.
Hammer gets confused sometimes 
If you wanna post your .vmf file, I or someone can take a look for you if you cant find it...
Rob.
This happens to many many people, and the problem 80% of the time is they have that button that hass a R with a red circle around it enabled. Its on the upper middle toolbar. Make sure that it isnt enabled. I think its called culling???
Mapping Since May 21, 2011
I was going to say the same thing. And it is called the 'radius culling' button, a cousin to the cordon tool.