Hi guys. I had exact the same problem: brink was launching only on sidebar and after a while "brink stopped working"
I was trying a bit with my graphic card drivers (Gigabyte Ati Radeon HD4850) and somehow I managed to fix the problem for me!
So I clicked in my CCC to "look for new drivers" and I was redirected to this page http://support.amd.com/us/gpudownload/Pages/index.aspx?src=http://forums.bethsoft.com/index.php?/topic/1187563-brink-crashes-on-startup/CCC-CheckForDriverUpdates
my card wasn't produced by amd, but I thought to myself what the hell, I just made format c yesterday, so I have nothing to lose.
I filled all information and as result I was here: http://sites.amd.com/us/game/downloads/Pages/radeon_vista-64.aspx
I downloaded Catalyst Software Suite 11.5 (first link, 85.1 MB size) installed it and... I lost avaibility to watch yt movies (green screen everywhere)... O.o
But I decided to launch game anyways and it works! I played first two missions, optimisation is a bit choppy, but game is playable.
About youtube videos problem - it disappeared after a simple pc reboot. Now both yt and Brink are working for me

I hope it'll help at least some of you, if not all... If so, give a plus or something to this post, so others can see it.
Ps. Is it only me, or every Brink copy has "Games for Windows" logo and uses Steam? It's kinda strange for me... o.O
Ps.2. My pc's main specification: Quad Core Q6600, Radeon HD 4850, 4gb ram