Almost exactly the same thing happened to me - marginal RAM in an old style macbook pro. Drove me absolutely crazy. People always talk about cosmic rays as wha

Almost exactly the same thing happened to me - marginal RAM in an old style macbook pro. Drove me absolutely crazy. People always talk about cosmic rays as what ECC is guarding against - not at all! It's shitty RAM, especially in laptops. When it's under stress.. for example buffering files in a large copy.. and you find out months later when it's too late to fix it. Not "theoretical" at all.