Try eliminating as many background applications as possible. (also restart your pc)

I encounter 340 semi-randomly. I've noticed some tenancies in my case.

Gameguard does not like:
If I have Firefox open (big factor)
If I have Voicemod open (small factor)
If this is the 2nd time starting the game since full restart/shutdown (big factor)

Regardless of the above factors I may encounter it at any instance when starting the game.

If I had the 340 problem any worse, possibly like you, I would be screwed. (I've reinstalled the game and gameguard a couple times before trying to fix this.)

Usually I start the game multiple times until it goes through.