Unconscious

I have reformatted my computer and am currently trying to play DayZ from a fresh install. It worked brilliantly before I had reformatted, but now I'm a bit stumped as to what to do. Whenever I try to play DayZ (via Six Launcher OR Day Z Commander), the loading of the server is interupted by the error message "the semaphore timeout period has expired", and I have to CTRL-ALT-DELETE the process. None of my other games do this, and I've reinstalled several times, it also worked absolutely fine before I reformatted the computer. (So it's not a hardware problem AFAIK) Any suggestions as to what might be causing it?

Still having some problems with this. I've tried updating all of my drivers - all of which are up to date. Day Z Commander won't even launch the game, it just hangs - Play WithSIX will launch it, but upon logging into the server it'll get stuck and after CTRL-ALT-DEL to desktop I see it's thrown up the Semaphore error. I've updated all drivers, uninstalled .net 4 and installed .net 4.5, I've run Chkdsk and it's all coming back clear... Steam can play both Arma games without error, it's only affecting DAY Z. (Verifying the integrity is fine also)

That's quite unlikely I imagine, as I'm running the same drivers as before the format (where it worked perfectly). I'm running the latest GTX 280 drivers.

Thanks for the responses. Chkdsk has been run several times - both from the elevated command prompt in the Windows Install Disk, and from within the OS during a restart. Found no errors. I just realized I have Microsoft .net Framework 4 installed, so I'll try getting rid of it and seeing what happens.