I like to keep people guessing.
But the compiler problem wasn't actually a compiler problem. I feel like an idiot, but it was just problem with the map causing bsp to fail instantly.
Once I figured that out, it turned out to just be a displacement that had accidentally gotten tied to an entity. So now I've got leaks and area portals not touching two areas. My spider sense tells me that one is causing the other but I'm not sure which way it goes...
EDIT: THE MAP COMPILES!! WOOT! It was a really clean compile too, with none of the bitchy little leaf portal errors or things like that. The map was over the max brush limit, but the rooms I removed from the 2nd section brought it back under the limit. There's still a ton to do but all the major hassles are gone (for the time being). Wahay!