I have similar problems. I don't suffer from long loading times, but since I entered act 2 and left Drifwood town, I'm crashing to desktop every 2 minutes. The crash message mentiones a memory issue. I didn't have any problems in act 1. The game is no longer playable.
I don't know much about pc's, but I tried lowering the resolution, disabled steam overlay and autosaves, and I updated my drivers. None of those things worked. I've read somethings here about overclocking, but I don't know what that means, so I assume my pc is not set up that way. I also have no mods installed.