update: yesterday I tried the support rodopoli mission but it crashed again.
It looks like that only the Helicopter missions on altis forces the crashs (I was able to play the stratis support mission over one hour without a crash)

update: looks like it's fixed in the last 1.4* versions

added another crash dump:
arma3_2013-09-29_12-27-21.zip

in this case 10 out of 16 players on the server got a CtD, all with the PhysX3_x86.dll error in the event log.

have someone played around with the Physx settings in the Nvdia control panel? (automatic, GPU, CPU?) I heared about that arma can only compute Physx by CPU because of its own library

same here... only tested in multiplayer

specs edit:
Geforce 570 GTX on 327.23 Nvidia Driver

2nd edit:
uploaded my two crash dumps and dxdiag
arma3_2013-09-28_12-13.zip

signed and up voted!

this would be a very nice "feature" to Arma 3.
I also have to switch from speakers to headset (USB) very often and it's realy annoying to restart the whole game everytime...