Yup, did the same thing for me just a moment ago. Joined a server, joined a position in a squad, click ago, received the files and then hanged at the load screen.

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.

Disregard this ticket, issue was caused by a ported over version of Bluecomm.

Sometimes the mission files make the game go boomboom. Just delete the mission files from the documents folder and allow the game to redownload them.

C:\Documents\Arma 3 Alpha - Other Profiles\<profilename>\Saved\mpmissions

Seems to be resolved.