I created this chamber in the Puzzle Maker (PeTI), and it looks okay, but I wanted to add a bottomless pit to it. So far so good. I left a placeholder pool of goo where I wanted the pit so that the activation decals of the buttons wouldn't decide to wander off to the depths below, compiled, then exported the file.

I open it on Hammer, it works perfectly well, I can even playtest it. Then I test deleting one of the textures of the goo, and I test, and once again it works, and the place where I deleted the goo has an ugly square with the typical 'nodraw' echo of images.

Then I started happily deleting all the other goo textures everywhere, leaving only the trigger blocks which I'd planned on editing later to turn them into deadly pits. After I finished the first room, I tried to test it and... suddenly I could no longer even leave the elevator instance where you start, getting this error:

prop_portal_linked_door '@entrance_portal_elevator_side' failed to link to partner named: '@entrance_portal_chamber_side'

But I did not touch anything anywhere near the elevator instances. What on earth is going on and how do I fix it?

Thank you in advance.

Verify game cache?
did you delete the exit corridors?
and did you delete one of the elevators?

Already verified the cache, and the only things I deleted were the long boxes that read 'nodraw' on their sides and had a shiny texture on top, i.e. the textures of the goo. The trigger is still there, unchanged.

maybe post your vmf?

http://www.4shared.com/file/D8uNDxhI/lasers.html

There is the vmf.

I can't find the entry door hallway, you might want to try to re-add the instance.