Hello. I have some further information that might help diagnose this issue and I'm posting here instead of starting a new thread as removing the mentioned KB updates solved the issue for me as well.
The issue I experienced was starting or previewing the stream would cause the the process selected in Game Capture to crash immediately with an Access Vidolation. (I have no OBS logs to provide as everything was fine from OBS' perspective and all the game logs showed no errors until the 0xc[bunch of 0s]5. Some games would run fine, others would crash immediately, others would work intermittently (eg. I was able to stream Outlast perfectly fine last night, but this morning [with no intervening reboot or even exiting OBS] it would crash immediately and I wasn't able to make it work again).
The access violation occurred pretty much the instant "SharedTexCapture hooked" appeared in the OBS log window.
The issue occurred using both 32 bit and 64 bit OBS capturing both 32 and 64 bit games with both the Catalyst Omega and last non-Omega Catalyst drivers (which worked perfectly previously) using all possible combinations of running game and/or OBS as administrator. In all cases the anti-cheat hooking made no difference and neither did switching between FullScreen, WindowedFullScreen or Windowed (as allowed by the various games).
Fraps and XSplit seem unaffected by these updates (Fraps was perfectly fine, XSplit's performance was horrible but I haven't checked it since OBS is working again heh).
Speculation: Something in those KB rollup updates affects game capture's ability to do its job, but it seems dependent on the engine's implementation as Guild Wars 2 (custom engine) was perfectly fine, yet Unreal (Outlast) would work intermittently and Unity-based games (DreadOut, The Forest, Rust) were a complete no-go.
Sorry for writing such a book but I bounced my head off this pretty much all weekend and figured it might help.
Edit: Oh yah, forgot: Windows 8.1 64-bit
