Also happens to me the exact same thing.

I'm 64 bit, Windows 7 Home Premium, I'm playing in Windowed with pretty much all settings to the Lowest or Disabled(GFX Settings) Except for Render Resolution, which is at 100%. I'm also trying to join a 60 player server and immediately after it's done loading the mission, it crashes before I can do anything.

Edit: It's not only 60 player server's, I'm attempting to join Wasteland servers.

Same symptoms as above, win7 64bit as well.

If anyone finds a way around this / fix then please tell because I would like to play. Thanks.

I may have (maybe) found a fix, I changed my resolution to match my total screen resolution, just scaled downwards because i'm in windowed, and switched it to that, and it seems to work, I've only joined succesfully once but i've only tried joining once since i changed my res, if you want to scale your resolution, i suggest going here: http://andrew.hedges.name/experiments/aspect_ratio/

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, so you can attach it here. Thank you.

I have attached the files from my folder :)

Not sure if I did it correctly, but I added my rar with the files from the folder.

I also experienced this problem , win7 64bit as well. Nvidia GTX 680, 314.14 Drivers. I've added my folder.

BTW: My Game also crashed once after changing the effects volume ^^

I've uploaded the requested files as well, after experiencing the issue as described by OP.

I did play successfully on a large server for about 5-10 minutes earlier before crashing. Since then I have had this issue.

Issue closed as obsolete. If you encounter this problem again, please create another ticket. Thank you.