Happens the same for me as Akheron described. The issue is definitely there on the Zeus 16+2 NATO Altis mission.

Place any unit then possess it. Cannot aim down sights.

One other issue associated with possession is if you use a unit and walk up to a body or a crate of some sort you cannot equip or move things from the crates/bodies/items to your inventory. It is as if your inventory is frozen.

Edit: Also Vanilla. I can provide video of both bugs if requested

Edit 2: It appears that since this mornings patch the aiming down sights bug is fixed. I tested it on Zeus 16+2 on Altis. The inventory thing still exists though. Will upload video in a minute

Edit 3: http://www.youtube.com/watch?v=fnCAsHXoo4A
I left in the lobby setup to show the settings I'm using for the game. Shows very clearly the inventory bug.

I just went to play more Zeus with a few friends and again cannot aim down sights. May be a multiplayer issue.

I have this issue as well. No weapon sight works. It does zoom in slightly but that's it.

A friend of mine who I play with consistently gets this issue after about 10 minutes of play. First it's running at about 30fps or so and then suddenly spikes downwards to 1fps or so. At this point he has to restart the game to fix it.

His specs are as follows

OS: Windows Vista Home Premium (32 bit)
Processor: Intel Core i5-2500 @ 3.30ghz (4 CPUs)
RAM: 3060MB RAM
GPU: GeForce GTX 480

Seems awful but he runs Stratis just fine for extended periods of time. Only on Altis does it do this. Scenario seems unrelated, happens on everything from a high action mission to just him and I spawning with one car to drive around. Exploration seems to inflame it.

A friend of mine, whom I play this with all the time, had the 0-2FPS bug on his system. It's 32bit Windows Vista. With todays patch, he is able to run Altis.. ..for about 2 minutes. It then degrades and goes back down to 0-2FPS. I have told him to add -maxmem=2400 to his command line when launching it, didn't seem to change too much.

I also see it. Chrome says ''Waiting for...'' for two websites. They are, and I'm not going to place a direct link, online1you.com and howtoplaycard.com

Site also asked me once to run Java. It's the same on www.bistudio.com - Bohemias home site.