Have you tried turning off scripts.txt battleye filter on the server? I've seen this with arma 2 a few times since April, when removing most of the contents of the scripts filter in battleye fixes it usually, but not a good idea. I talked with Bastian last time it happened and it was fixed with an update towards the end of April, but came back again in June. You'll usually see a bunch of memory errors in the client rpt if it's the same problem, and the arma client will be leaking memory. Could be something completely different though.