This is my Experience what happend and how i fixed it. I found no complete working Solution on Google and i want to share how i fixed it. If you got the Error in Hammer: "missing material editor/wireframe" There are 2 Checks/Fixes that i tried and worked...
1. Check Game Configurations
For me before i can´t open Hammer because i moved the game directory and the game configuration had the old Location after i edited <\bin\GameConfig.txt>, Hammer booted normally but... That happend (Step 2)
2. Check gameinfo.txt
The gameinfo.txt Is located in ex. (Counter-Strike Source\cstrike\). The thing is i compared the downloaded the original file and the downloaded one the original had more information than the downloaded gameinfo.txt what i did was that \/
My Experience downloaded an online gameinfo.txt
After the end, where i looked at most of the files. I removed the downloaded gameinfo.txt and after that it works.
3. Check if the FGD Files
picked up from other sources. There are 3 Files that a required to have it in the Game Configuration, They Are: base.fgd, yourgame.fgd and halflife2.fgd (optional) . If they not in the Game Configuration then add them if they not the fgd files no existing in the game folder then you need to get the game data.