TheWalker27, please use standard fonts and colors. Thanks.
btw: if you set ‘-game c:\Steam\SteamApps\sourcemods\BMS’ as launch params for the 2007 SDK, BMS starts (and crashes like before). did not know you could set absolute paths…
I found this, i dont get it but maybe someone of guys do! I think this could be a solution!
SetupArrayProps R: array prop ‘null’ is at index zero
The startup error SetupArrayProps R: array prop ‘null’ is at index zero is caused by trying to run a Source 2007 game/mod with the Source 2009 engine. This is not possible.
Solution
The only Source 2007 game left today is Source SDK Base 2007. To use it:
Change the SteamAppId value in gameinfo.txt to 218, then restart Steam.
Make sure that any paths to hl2.exe (such as the launch path for the Visual Studio debugger) are pointing to SteamApps/account_name/source sdk base 2007/hl2.exe.
If the SDK launcher lists any Source 2007 games, reset it for each engine version to prevent future confusion.
Use the SDK launcher’s “Edit Game Configurations” tool to move your mod’s SDK profile to Source 2007.
Tip: To access content from a 2009 game while still using the 2007 engine, see mounting multiple games.
Is this the real solution for us?
If so please someone tell me how to do it by myself!! 
Mine is already set to automatic updates, but still no change
The valve wikipage you cited has an edit timestamp much older than todays problem, tried it several hours ago because i wanted to play goddammit, did not help.
Well if you go to BMS folder and open steam.inf, there is one line of text in the file. I presume it says 218, just like it should.
Someone said that by setting Source SDK on to automatic update should fix the problem… It didn’t. There are still a lot of us stuck.
Hopefully this gets fixed, and the BM team COUGHreleases XenCOUGH
Has anyone tried downloading Source SDK Base 2013 Singleplayer and launching the mod using that? 
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Ah ok, well it was worth a try!
Thanks anyways!
Crossing my fingers for an update…
Alright guys: Right click Source SDK Base 2007, hit Preferences, then Betas, the Steampipe Beta in the drop down box.
Then try to verify file integrity. It will have it convert over to SteamPipe, after that is done Black Mesa will work again.
Do you mean verify integrity of tool cache?
Steams not letting me log in online, is this happening to anyone else?
Currently Doing this. It says i have to download some more content (400 mb more) will inform how this goes, when download finishes.
I have no idea why, but Steam automatically downloaded (half) Source SDK Base 2006. Is that really necessary for something? Also, downloading a patch for Source SDK Base 2007. Wondering if something changes …
But why does it download 2006? I didn’t requested it …
It absolutely works, if you lose connection to steam and can’t seem to get onto the network RESTART your PC. You’ll be able to log in normally and continue with verifying file integrity. After that it’s all set!
Thanks again for the fix guys!
I can confirm that this worked.
Well, ladies and gentlemen, confirmed, the new patch that Valve released fixed the issue, thanks for your support, and for reading this.
Have fun, later.
I am doing this now. If it works for me, I’ll provide a step-by-step instruction for those not as technologically savvy.
how did you download the patch?
Downloaded automatically as Steam started. You can try re-entering Steam, or by enter Black Mesa: Source. Hope this works.
So you didnt have to go to preferences on the sdk 2007 build and verify files?
Nope, just re-start Steam, and let it automatically download the patch.