I have a similar problem. After a period of gameplay (10 minutes up to 30) my game freezes. If I alt tab out, ctrl alt delete to get task manager up and just tab through my open windows over and over eventually it gets out of its funk and lets me resume normal play without the application closing.

We need dxdiag and files from this folder to solve your problem. C:\Users\<Name>\AppData\Local\Arma 3 Alpha\

Can you upload it somewhere in winrar package please?
If package is smaller than 5,000k, you can attach it here. Thank you.

Crash dump reports are very important to solve crashes.
You can find them on these locations:
Arma 3 Alpha: C:\Users\<Name>\AppData\Local\Arma 3 Alpha\
Arma 3 Alpha Lite: C:\Users\<Name>\AppData\Local\Arma 3 Alpha Lite\

Move all files from this folder and pack them in a RAR archive. Next, upload them to a free upload service like RapidShare.

Please try to reproduce the crash again; reproducible reports are very important for our ability to fix crashes.

Click on the "Report Issue" button in the navigation menu under the Arma 3 logo.

Fill in all the necessary information for reproducing the crash. In the "Steps to Reproduce" window describe step-by-step how to do so. Don't forget to provide the link to where the crash dumps are uploaded and the game version.
Please also attach your DxDiag file (http://en.wikipedia.org/wiki/DxDiag).

You can also attach the aforementioned files from the crash dump folder, but the attachment can't be bigger than 5000 KB.

Always keep the public View Status.
After all necessary information is filled out, save the report using the "Submit Report" button.

Ticket closed due to lack of information. If the issue is still valid, please create a new one including the required files listed in the how-to-guide (red button, top right) under "How to report a crash".