If you use any mods besides Twallans or AM, make sure they are up to date. Any time I have experienced crashing, it was due to an out of date mod that I had forgotten to update. Additionally, make sure your game and expansions are patched.
ETA: This advice assumes that this is not rig failure due to insufficient RAM/GPU/hard disk.
How would I know if its hard drive failure? Checking the other things the other mods I have.