Black screen/white box on launch - seems exclusive to gmod, directx issue? - Help

See Image here >> [URL="http://i.imgur.com/n1Vm6vJ.jpg"]http://i.imgur.com/n1Vm6vJ.jpg[/URL] So I posted on reddit a little while back with this issue and didn't really get a solution, other people have written about it around the web a little, but there doesn't seem to be a solution there either.. When I launch up gmod, I get the screen in the image above. This is fixed if I launch it in dxlevel 81, however.. I want to be able to play it in directx 9. I did manage to somehow get it fixed through a complete reinstall of gmod the other day, after getting a new graphics card. However, today I decided to upgrade to windows 8.1 and the problem has returned. What's strange is that occurs on both systems I have, a fresh install of 8.1 on this system, a relatively new install of 8.1 on a spare system, and it was occurring on my win7 machine before I upgraded.. [B][I]This tells me it's not the operating system.[/I][/B] Previously, I had both systems on a Radeon 6950 2gb, but I've since upgraded (just the other day) to have my main machine on a GTX 780 3gb. I did initially still have the issue, then I got it fixed, then I was stupid enough to do a fresh install of windows, as I was having other unrelated issues I wanted to solve. [B][I]This tells me it's not the graphics card[/I][/B], and I'd make a call that it's not the drivers either, I've tried reinstalling and whatnot, still nothing. I thought it might've been about making a fresh install of gmod after installing drivers, but nope, didn't seem to do it. My two different systems have different cpus, different motherboards, different graphics cards (now), they previously had different os'es (7 and 8) different ram, fresh installs without messing them around. By process of elimination, I'm not sure what I have left to do. It seems to be directly an issue with directx and garry's mod, it's not a problem with counter strike source, or tf2, or hl2, or any other game. As I said, it also runs fine in dxlevel 81, but if you try run it in 90/95, it seems like it doesn't even get to the menu, let alone see it, it doesn't make any noise if you move your mouse around like it would if the menu worked.. I'm tearing my hair out about it, I just wanna play gmod and it's made so difficult! asrock z77extreme4 i7 3770k 12gb ram windows 8.1 (previously 7, same problem) Gigabyte GTX 780 (previously a 6950 2gb, same problem)

Check out this article: [url]http://support.facepunchstudios.com/kb/articles/6-i-get-crashes-on-start-or-the-screen-is-just-black[/url]

I did, as I said, dxlevel 81 gets it to work.. but it doesn't work when you try put it back to dxlevel 90/95

Nowhere in that article it says to put -dxlevel 81 to your launch options.

right.. I'm getting confused with what I've read, but I did go through that originally (I did google around) I did do the autoconfig, the windowed, verified game cache, verified tf2, disabled windows firewall (only antivirus I've got)..

So I don't know why, but deleting local content, and then deleting the folder, then redownloading and reinstalling.. that worked.