Yeah I haven't heard reports of those bugs else where. Are your video drivers up to date? You may want to try the most recent beta drivers, and if your video cards overclocked try setting it back to defaults. I played the game for about 25 hours and didn't experience any of the problems you're describing.
Video drivers aren't going to play in to what he's describing. He has a ruined save game at this point from a game bug. It can happen. It sucks when it does. That's really part of why I have daily backups of my systems. If I encounter something like this, I can just restore whatever state I had 24 hours prior. It sounds like in his case, he played a scene that restricts you to a single weapon (there are a few) and the game's mechanism for doing that is to remove all your other items, and then add them back when that scene is over. It apparently didn't add his back.
You always need backups of anything you find important, and save files, in a way, are.
The only bug like that I've had is when I had a mission to go to a place, kill 3 people, and take their pictures, I killed one of the three before I triggered the "you are at the place" checkpoint, and it didn't count him as dead. Once I killed the other two, it realized he was dead, and told me to take pictures, but I could never take pictures of that first dead guy. Of course, I just reset the mission. In his case, once he saved (Which it likely auto-saved when he finished), he was screwed.