I just made a new chamber sign using the Raw Level Signage thing found here. I followed the thing EXCALTY, even down to copying the name for the vtf. But, when I try to place it in Hammer, I get the texture error thing. The texture icon shows up, and when I loaded up the file in Photoshop, it showed the first frame, so it should be showing up. Here's the vmt:

"LightmappedGeneric"
{   
   "$baseTexture" "cham1_level_sign"
   "$surfaceprop" "glass"
   "$selfillum" 1
   "%keywords" "portal"
   "%noportal" 1
   "Proxies"
   {
      "ToggleTexture"
      {
         "toggleTextureVar" "$baseTexture"
                     "toggleTextureFrameNumVar" "$frame"
                     "toggleTextureShouldWrap" "0"
      }
   }
}

Any help?

EDIT: Okay, I got the texture error to go away, but now the texture's just transparent. None of it's showing up.

2 questions. One will probably insult you if it doesn't help.

First: Do you have an Alpha Channel in your .vtf?
Second: You are specifying the correct texture location... right? (It needs to have sub-folders in materials as well ie, materials/examplefolder/texturefilehere would correspond with examplefolder/texturefilehere in the .vmt. If that makes sense.
Other than those, I can't see anything wrong with the .vmt. It looks exactly like mine do!!

1. Yes, I have an Alpha Channel in it.
2. What do you mean by that? Do you mean that the .vmt has to be in the same folder as the .vtf? If so, then yes.