Fell through the game, help!!!!

[big1r1shbastard]

Like others I'm in a glitch where I can walk through walls and basically go where ever I want. It's not as cool as it sounds and has made the game unplayable.
Unlike the others with this problem my computer saviness is limited and I have no idea what they're talking about in their posts.
It would be most appreciated if someone could give me detailed info on how to get out of this "ghost" mode.
Thankyou for your time.