Posted by aerial
You need to compile your cubemaps with both HDR enabled and disabled.
He did, he wrote.
I had a similar problem, I solved it by lowering the Specs to mid or low (shader detals and stuff),
then I do buildcubemaps.
And the it worked fine for me once I set the settings high again.
By the way:
If you're not using any console commands, you cannot turn off HDR in left4dead and basically there is no need to make LDR ones too since it just increases the filesize for something no one will see anyway.
Posted by traggey
Thank you DamageFilter! By changing my settings to Normal, i can no longer see the error textures, however if doesn't work compiling it on normal and then go high again, it goes back to checkerbox.
That's because his method is incorrect. Setting your settings to normal or low removes specular mapping.