I told myself I'd never do this. I would use my ultimate ninja skills, and if all else fails I would find it without posting. So much for that. Let's just say I have a map, that's a sequel to a pretty popular map, that is the sequel to a kinda sort of not really popular map...I am using a custom texture for the test chamber sign (I think I might post a tutorial since I've never seen it done the way I'm doing it), and it loads into Hammer fine, and the animation entities that I set up for it work like a charm. But when I close and reopen Hammer, the texture is replace with good ol' purple checkers. It finds the texture, but it defaults to 64x64 pink checkers. If I don't touch it, the texture recompiles fine. If I go into the texture browser, browse to my texture, and click reload, it turns into a version of my texture that's 64x64 (my texture is 512 x 1024, so it's not even square), and the thumbnail goes completely white. If I choose to fit my texture (or edit it's allignment in some other way) and then reload again, it fixes itself. It's not that big of a deal, since I technically can just ignore it, but it's annoying, distracting, and makes editing a room with this texture difficult. I've never seen or heard of this happening. Any ideas?

3rd copy of this topic...

EDIT: Oh, that copy... how'd that happen?!? I swear I didn't do that...

EDIT2: How is there FOUR copies of this?

I got it figured out. I thought I would share my findings, just in case someone else runs over this same problem. Take a look at these two VMT files. The first is a fairly standard metal material, the second is my custom material:
"materials/metal/black_metal_floor_001a.vmt"
||LightMappedGeneric
{
$basetexture "metal/black_floor_metal_001a"
$bumpmap "metal/black_floor_tile_001c_height-ssbump"
$ssbump 1
$reflectivity "[ 0.6 0.6 0.6 ]"
$envmap "metal/black_wall_envmap_002a"
hdr
{
$envmap "metal/black_wall_envmap_002a_hdr"
}
$envmaplightscale 0.6

$normalmapalphaenvmapmask 1
$envmapcontrast 1.0
$envmapsaturation 0.2
$envmaptint 0.3 0.3 0.3
"%noportal" 1
$detail "detail/detail_blackfloor"
$detailscale 4.2
$detailblendfactor .6
$detailblendmode 7
"%keywords" "portal2 noportal chamber"
}||
"materials/lightofday/{SPOILER}/{SPOILER}.vmt"
||LightMappedGeneric
{
$basetexture lightofday/{SPOILER}/{SPOILER}.vtf
$surfaceprop glass
$selfillum 1

$frame      0

"%noportal"   1
"%keywords"   "testsign chamber [SPOILER]"

Proxies
{
    ToggleTexture
    {
        toggleTextureVar            $basetexture
        toggleTextureFrameNumVar        $frame
        toggleShouldWrap            0
    }
}

}||
Notice the difference? Well I didn't.

Sorry for cluttering the forums. If I knew what happened I would say I won't do it again, but I'm afraid I'm not quite sure what happened. Thanks for you support.

Dude, to be honest, this is a real mess of topic >.<

Not even your final conclusions do lead to any understanding of the problem or the solution for it

I'm not sure if you wanted to make a custom texture toogleable, like the indicator lights, or a lightboard custom texture, and that stock texture for the typical P2's black floor has nothing to do with any of those...

Can you please explain all of this clearly in order to let ppl that reads it understand it before posting any tutorial here? thanks!

I think that he just forgot to change the vmt.

The problem has absolutely nothing to do with the texture I was making or the light board tutorial I will be making. It's simply that, as you can see by the bolded lines, I added ".vtf" to the end of the texture path. This works just fine for Portal, but Hammer chokes on them, requiring a little prompting to get the texture to load. Removing the ".vtf" makes everything work as expected. The tutorial will be more of a "here's how to make everything look like the original signs" then a ground-breaking revelation. I will link to it from here if anyone's interested.